diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 5db68d3cb4..48eaf3f60f 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -878,6 +878,23 @@ export def FTsig()
   endif
 enddef
 
+# This function checks the first 100 lines of files matching "*.sil" to
+# resolve detection between Swift Intermediate Language and SILE.
+export def FTsil()
+  for lnum in range(1, [line('$'), 100]->min())
+    var line: string = getline(lnum)
+    if line =~ '^\s*[\\%]'
+      setf sile
+      return
+    elseif line =~ '^\s*\S'
+      setf sil
+      return
+    endif
+  endfor
+  # no clue, default to "sil"
+  setf sil
+enddef
+
 export def FTsys()
   if exists("g:filetype_sys")
     exe "setf " .. g:filetype_sys
diff --git a/runtime/doc/map.txt b/runtime/doc/map.txt
index 69557d6146..6beae6ee2c 100644
--- a/runtime/doc/map.txt
+++ b/runtime/doc/map.txt
@@ -1724,11 +1724,11 @@ The valid escape sequences are
 					*<mods>* *<q-mods>* *:command-modifiers*
 	<mods>  The command modifiers, if specified. Otherwise, expands to
 		nothing. Supported modifiers are |:aboveleft|, |:belowright|,
-		|:botright|, |:browse|, |:confirm|, |:hide|, |:keepalt|,
-		|:keepjumps|, |:keepmarks|, |:keeppatterns|, |:leftabove|,
-		|:lockmarks|, |:noautocmd|, |:noswapfile| |:rightbelow|,
-		|:sandbox|, |:silent|, |:tab|, |:topleft|, |:unsilent|,
-		|:verbose|, and |:vertical|.
+		|:botright|, |:browse|, |:confirm|, |:hide|, |:horizontal|,
+		|:keepalt|, |:keepjumps|, |:keepmarks|, |:keeppatterns|,
+		|:leftabove|, |:lockmarks|, |:noautocmd|, |:noswapfile|
+		|:rightbelow|, |:sandbox|, |:silent|, |:tab|, |:topleft|,
+		|:unsilent|, |:verbose|, and |:vertical|.
 		Note that |:filter| is not supported.
 		Examples: >
 		    command! -nargs=+ -complete=file MyEdit
diff --git a/runtime/doc/term.txt b/runtime/doc/term.txt
index 7acfba78c6..906e44404d 100644
--- a/runtime/doc/term.txt
+++ b/runtime/doc/term.txt
@@ -643,6 +643,18 @@ Example for an xterm, this changes the color of the cursor: >
     endif
 NOTE: When Vim exits the shape for Normal mode will remain.  The shape from
 before Vim started will not be restored.
+
+For Windows Terminal you can use something like this: >
+    " Note: This should be set after `set termguicolors` or `set t_Co=256`.
+    if &term =~ 'xterm' || &term == 'win32'
+	" Use DECSCUSR escape sequences
+	let &t_SI = "\e[5 q"    " blink bar
+	let &t_SR = "\e[3 q"    " blink underline
+	let &t_EI = "\e[1 q"    " blink block
+	let &t_ti ..= "\e[1 q"   " blink block
+	let &t_te ..= "\e[0 q"   " default (depends on terminal, normally blink block)
+    endif
+
 {not available when compiled without the |+cursorshape| feature}
 
 							*termcap-title*
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index b77b789a2c..aba0f0051e 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1618,7 +1618,7 @@ type, it can not be used in Vim9 script.
 			 *E1211* *E1217* *E1218* *E1219* *E1220* *E1221*
 			 *E1222* *E1223* *E1224* *E1225* *E1226* *E1227*
 			 *E1228* *E1238* *E1250* *E1251* *E1252* *E1253*
-			 *E1256* *E1297*
+			 *E1256* *E1297* *E1298*
 Types are checked for most builtin functions to make it easier to spot
 mistakes.
 
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index c2b89a5f80..c7670d08ca 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -1822,7 +1822,7 @@ au BufNewFile,BufRead *.score			setf slrnsc
 au BufNewFile,BufRead *.st			setf st
 
 " Smalltalk (and Rexx, TeX, and Visual Basic)
-au BufNewFile,BufRead *.cls                     call dist#ft#FTcls()
+au BufNewFile,BufRead *.cls			call dist#ft#FTcls()
 
 " Smarty templates
 au BufNewFile,BufRead *.tpl			setf smarty
@@ -1929,8 +1929,8 @@ au BufNewFile,BufRead *.cm			setf voscm
 au BufNewFile,BufRead *.swift			setf swift
 au BufNewFile,BufRead *.swift.gyb		setf swiftgyb
 
-" Swift Intermediate Language
-au BufNewFile,BufRead *.sil			setf sil
+" Swift Intermediate Language or SILE
+au BufNewFile,BufRead *.sil			call dist#ft#FTsil()
 
 " Sysctl
 au BufNewFile,BufRead */etc/sysctl.conf,*/etc/sysctl.d/*.conf	setf sysctl
diff --git a/src/channel.c b/src/channel.c
index f185023765..d154ff2a84 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -2757,12 +2757,8 @@ channel_exe_cmd(channel_T *channel, ch_part_T part, typval_T *argv)
     }
     else if (STRCMP(cmd, "redraw") == 0)
     {
-	exarg_T ea;
-
 	ch_log(channel, "redraw");
-	CLEAR_FIELD(ea);
-	ea.forceit = *arg != NUL;
-	ex_redraw(&ea);
+	redraw_cmd(*arg != NUL);
 	showruler(FALSE);
 	setcursor();
 	out_flush_cursor(TRUE, FALSE);
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index e160b60907..42f9c32658 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -1776,6 +1776,7 @@ set_context_by_cmdname(
 	case CMD_folddoclosed:
 	case CMD_folddoopen:
 	case CMD_hide:
+	case CMD_horizontal:
 	case CMD_keepalt:
 	case CMD_keepjumps:
 	case CMD_keepmarks:
diff --git a/src/errors.h b/src/errors.h
index befc8eeb36..7846a0728a 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3323,5 +3323,9 @@ EXTERN char e_cannot_specify_both_type_and_types[]
 EXTERN char e_can_only_use_left_padding_when_column_is_zero[]
 	INIT(= N_("E1296: Can only use left padding when column is zero"));
 #endif
+#ifdef FEAT_EVAL
 EXTERN char e_non_null_dict_required_for_argument_nr[]
 	INIT(= N_("E1297: Non-NULL Dictionary required for argument %d"));
+EXTERN char e_non_null_list_required_for_argument_nr[]
+	INIT(= N_("E1298: Non-NULL List required for argument %d"));
+#endif
diff --git a/src/eval.c b/src/eval.c
index 2e8d938ec6..f55d9de8ec 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -6729,7 +6729,8 @@ ex_execute(exarg_T *eap)
 
     ga_init2(&ga, 1, 80);
 #ifdef HAS_MESSAGE_WINDOW
-    in_echowindow = (eap->cmdidx == CMD_echowindow);
+    if (eap->cmdidx == CMD_echowindow)
+	start_echowindow();
 #endif
 
     if (eap->skip)
@@ -6833,17 +6834,7 @@ ex_execute(exarg_T *eap)
 	--emsg_skip;
 #ifdef HAS_MESSAGE_WINDOW
     if (eap->cmdidx == CMD_echowindow)
-    {
-	// show the message window now
-	ex_redraw(eap);
-
-	// do not overwrite messages
-	// TODO: only for message window
-	msg_didout = TRUE;
-	if (msg_col == 0)
-	    msg_col = 1;
-	in_echowindow = FALSE;
-    }
+	end_echowindow();
 #endif
     set_nextcmd(eap, arg);
 }
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 01872f8d4c..14cb770efe 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3235,11 +3235,8 @@ f_call(typval_T *argvars, typval_T *rettv)
 		|| check_for_opt_dict_arg(argvars, 2) == FAIL))
 	return;
 
-    if (argvars[1].v_type != VAR_LIST)
-    {
-	emsg(_(e_list_required));
+    if (check_for_list_arg(argvars, 1) == FAIL)
 	return;
-    }
     if (argvars[1].vval.v_list == NULL)
 	return;
 
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index a514098c6a..7f7ea4bcbc 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2461,6 +2461,7 @@ do_one_cmd(
 	    case CMD_final:
 	    case CMD_help:
 	    case CMD_hide:
+	    case CMD_horizontal:
 	    case CMD_ijump:
 	    case CMD_ilist:
 	    case CMD_isearch:
@@ -8356,10 +8357,19 @@ ex_redir(exarg_T *eap)
 }
 
 /*
- * ":redraw": force redraw
+ * ":redraw": force redraw, with clear for ":redraw!".
  */
     void
 ex_redraw(exarg_T *eap)
+{
+    redraw_cmd(eap->forceit);
+}
+
+/*
+ * ":redraw": force redraw, with clear if "clear" is TRUE.
+ */
+    void
+redraw_cmd(int clear)
 {
     int		r = RedrawingDisabled;
     int		p = p_lz;
@@ -8368,7 +8378,7 @@ ex_redraw(exarg_T *eap)
     p_lz = FALSE;
     validate_cursor();
     update_topline();
-    update_screen(eap->forceit ? UPD_CLEAR : VIsual_active ? UPD_INVERTED : 0);
+    update_screen(clear ? UPD_CLEAR : VIsual_active ? UPD_INVERTED : 0);
     if (need_maketitle)
 	maketitle();
 #if defined(MSWIN) && (!defined(FEAT_GUI_MSWIN) || defined(VIMDLL))
diff --git a/src/filepath.c b/src/filepath.c
index d840d88c95..a316a96abe 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -1603,19 +1603,20 @@ readdir_checkitem(void *context, void *item)
     return checkitem_common(context, name, NULL);
 }
 
+/*
+ * Process the keys in the Dict argument to the readdir() and readdirex()
+ * functions.  Assumes the Dict argument is the 3rd argument.
+ */
     static int
-readdirex_dict_arg(typval_T *tv, int *cmp)
+readdirex_dict_arg(typval_T *argvars, int *cmp)
 {
     char_u     *compare;
 
-    if (tv->v_type != VAR_DICT)
-    {
-	emsg(_(e_dictionary_required));
+    if (check_for_nonnull_dict_arg(argvars, 2) == FAIL)
 	return FAIL;
-    }
 
-    if (dict_has_key(tv->vval.v_dict, "sort"))
-	compare = dict_get_string(tv->vval.v_dict, "sort", FALSE);
+    if (dict_has_key(argvars[2].vval.v_dict, "sort"))
+	compare = dict_get_string(argvars[2].vval.v_dict, "sort", FALSE);
     else
     {
 	semsg(_(e_dictionary_key_str_required), "sort");
@@ -1660,7 +1661,7 @@ f_readdir(typval_T *argvars, typval_T *rettv)
     expr = &argvars[1];
 
     if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN &&
-	    readdirex_dict_arg(&argvars[2], &sort) == FAIL)
+	    readdirex_dict_arg(argvars, &sort) == FAIL)
 	return;
 
     ret = readdir_core(&ga, path, FALSE, (void *)expr,
@@ -1713,7 +1714,7 @@ f_readdirex(typval_T *argvars, typval_T *rettv)
     expr = &argvars[1];
 
     if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN &&
-	    readdirex_dict_arg(&argvars[2], &sort) == FAIL)
+	    readdirex_dict_arg(argvars, &sort) == FAIL)
 	return;
 
     ret = readdir_core(&ga, path, TRUE, (void *)expr,
diff --git a/src/insexpand.c b/src/insexpand.c
index 0953342171..08cbf5c068 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -2934,9 +2934,7 @@ f_complete(typval_T *argvars, typval_T *rettv UNUSED)
     if (!undo_allowed())
 	return;
 
-    if (argvars[1].v_type != VAR_LIST || argvars[1].vval.v_list == NULL)
-	emsg(_(e_invalid_argument));
-    else
+    if (check_for_nonnull_list_arg(argvars, 1) != FAIL)
     {
 	startcol = (int)tv_get_number_chk(&argvars[0], NULL);
 	if (startcol > 0)
@@ -3147,11 +3145,8 @@ f_complete_info(typval_T *argvars, typval_T *rettv)
 
     if (argvars[0].v_type != VAR_UNKNOWN)
     {
-	if (argvars[0].v_type != VAR_LIST)
-	{
-	    emsg(_(e_list_required));
+	if (check_for_list_arg(argvars, 0) == FAIL)
 	    return;
-	}
 	what_list = argvars[0].vval.v_list;
     }
     get_complete_info(what_list, rettv->vval.v_dict);
diff --git a/src/list.c b/src/list.c
index 5e70f2111b..c9697e0514 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1519,11 +1519,8 @@ f_join(typval_T *argvars, typval_T *rettv)
 		|| check_for_opt_string_arg(argvars, 1) == FAIL))
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_list_required));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
 
     if (argvars[0].vval.v_list == NULL)
 	return;
@@ -1728,11 +1725,8 @@ f_list2str(typval_T *argvars, typval_T *rettv)
 		|| check_for_opt_bool_arg(argvars, 1) == FAIL))
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_invalid_argument));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
 
     l = argvars[0].vval.v_list;
     if (l == NULL)
diff --git a/src/match.c b/src/match.c
index 335b06011f..ebdaeabcff 100644
--- a/src/match.c
+++ b/src/match.c
@@ -1087,11 +1087,8 @@ f_setmatches(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
 		|| check_for_opt_number_arg(argvars, 1) == FAIL))
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_list_required));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
     win = get_optional_window(argvars, 1);
     if (win == NULL)
 	return;
diff --git a/src/mbyte.c b/src/mbyte.c
index 73065c7394..54f7fa4fbb 100644
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -5535,14 +5535,9 @@ f_setcellwidths(typval_T *argvars, typval_T *rettv UNUSED)
     size_t	    cw_table_size_save;
     char	    *error = NULL;
 
-    if (in_vim9script() && check_for_list_arg(argvars, 0) == FAIL)
+    if (check_for_nonnull_list_arg(argvars, 0) == FAIL)
 	return;
 
-    if (argvars[0].v_type != VAR_LIST || argvars[0].vval.v_list == NULL)
-    {
-	emsg(_(e_list_required));
-	return;
-    }
     l = argvars[0].vval.v_list;
     if (l->lv_len == 0)
     {
diff --git a/src/message.c b/src/message.c
index 3a8d857ba7..eceaca5099 100644
--- a/src/message.c
+++ b/src/message.c
@@ -1448,7 +1448,7 @@ msg_start(void)
     }
 
 #ifdef FEAT_EVAL
-    if (need_clr_eos || in_echowindow)
+    if (need_clr_eos)
     {
 	// Halfway an ":echo" command and getting an (error) message: clear
 	// any text from the command.
@@ -3651,6 +3651,10 @@ msg_clr_eos(void)
     void
 msg_clr_eos_force(void)
 {
+#ifdef HAS_MESSAGE_WINDOW
+    if (in_echowindow)
+	return;  // messages go into a popup
+#endif
     if (msg_use_printf())
     {
 	if (full_screen)	// only when termcap codes are valid
diff --git a/src/os_win32.c b/src/os_win32.c
index f06227f10a..f6bf91d9fa 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -213,6 +213,7 @@ static int g_color_index_bg = 0;
 static int g_color_index_fg = 7;
 
 # ifdef FEAT_TERMGUICOLORS
+static int default_console_color_bg = 0x000000; // black
 static int default_console_color_fg = 0xc0c0c0; // white
 # endif
 
@@ -1527,13 +1528,27 @@ decode_mouse_event(
     static void
 mch_set_cursor_shape(int thickness)
 {
-    CONSOLE_CURSOR_INFO ConsoleCursorInfo;
-    ConsoleCursorInfo.dwSize = thickness;
-    ConsoleCursorInfo.bVisible = s_cursor_visible;
+    if (USE_VTP || USE_WT)
+    {
+	if (*T_CSI == NUL)
+	{
+	    // If 't_SI' is not set, use the default cursor styles.
+	    if (thickness < 50)
+		vtp_printf("\033[3 q");	// underline
+	    else
+		vtp_printf("\033[0 q");	// default
+	}
+    }
+    else
+    {
+	CONSOLE_CURSOR_INFO ConsoleCursorInfo;
+	ConsoleCursorInfo.dwSize = thickness;
+	ConsoleCursorInfo.bVisible = s_cursor_visible;
 
-    SetConsoleCursorInfo(g_hConOut, &ConsoleCursorInfo);
-    if (s_cursor_visible)
-	SetConsoleCursorPosition(g_hConOut, g_coord);
+	SetConsoleCursorInfo(g_hConOut, &ConsoleCursorInfo);
+	if (s_cursor_visible)
+	    SetConsoleCursorPosition(g_hConOut, g_coord);
+    }
 }
 
     void
@@ -6769,6 +6784,21 @@ notsgr:
 	    }
 # endif
 	}
+	else if (s[0] == ESC && len >= 3-1 && s[1] == '[')
+	{
+	    int l = 2;
+
+	    if (isdigit(s[l]))
+		l++;
+	    if (s[l] == ' ' && s[l + 1] == 'q')
+	    {
+		// DECSCUSR (cursor style) sequences
+		if (USE_VTP || USE_WT)
+		    vtp_printf("%.*s", l + 2, s);   // Pass through
+		s += l + 2;
+		len -= l + 1;
+	    }
+	}
 	else
 	{
 	    // Write a single character
@@ -7878,6 +7908,13 @@ vtp_init(void)
     store_console_fg_rgb = save_console_fg_rgb;
 
 # ifdef FEAT_TERMGUICOLORS
+    if (!USE_WT)
+    {
+	COLORREF bg;
+	bg = (COLORREF)csbi.ColorTable[g_color_index_bg];
+	bg = (GetRValue(bg) << 16) | (GetGValue(bg) << 8) | GetBValue(bg);
+	default_console_color_bg = bg;
+    }
     fg = (COLORREF)csbi.ColorTable[g_color_index_fg];
     fg = (GetRValue(fg) << 16) | (GetGValue(fg) << 8) | GetBValue(fg);
     default_console_color_fg = fg;
@@ -7945,7 +7982,7 @@ vtp_sgr_bulks(
     if (argc == 0)
     {
 	sgrfgr = sgrbgr = -1;
-	vtp_printf("033[m");
+	vtp_printf("\033[m");
 	return;
     }
 
@@ -8160,11 +8197,20 @@ get_default_console_color(
 	ctermbg = -1;
 	if (id > 0)
 	    syn_id2cterm_bg(id, &ctermfg, &ctermbg);
-	cterm_normal_bg_gui_color = guibg =
+	if (!USE_WT)
+	{
+	    guibg = ctermbg != -1 ? ctermtoxterm(ctermbg)
+						    : default_console_color_bg;
+	    cterm_normal_bg_gui_color = guibg;
+	    ctermbg = ctermbg < 0 ? 0 : ctermbg;
+	}
+	else
+	{
+	    cterm_normal_bg_gui_color = guibg =
 			    ctermbg != -1 ? ctermtoxterm(ctermbg) : INVALCOLOR;
-
-	if (ctermbg < 0)
-	    ctermbg = 0;
+	    if (ctermbg < 0)
+		ctermbg = 0;
+	}
     }
 
     *cterm_fg = ctermfg;
diff --git a/src/popupwin.c b/src/popupwin.c
index 8292dba32e..8688f3e3d1 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -1356,6 +1356,8 @@ popup_adjust_position(win_T *wp)
 
     if (wp->w_maxheight > 0)
 	maxheight = wp->w_maxheight;
+    else if (wp->w_popup_pos == POPPOS_BOTTOM)
+	maxheight = cmdline_row - 1;
 
     // start at the desired first line
     if (wp->w_firstline > 0)
@@ -4479,6 +4481,7 @@ popup_get_message_win(void)
 	message_win->w_popup_pos = POPPOS_BOTTOM;
 	message_win->w_wantcol = 1;
 	message_win->w_minwidth = 9999;
+	message_win->w_firstline = -1;
 
 	// no padding, border at the top
 	for (i = 0; i < 4; ++i)
@@ -4529,6 +4532,31 @@ popup_hide_message_win(void)
 	popup_hide(message_win);
 }
 
+/*
+ * Invoked before outputting a message for ":echowindow".
+ */
+    void
+start_echowindow(void)
+{
+    in_echowindow = TRUE;
+}
+
+/*
+ * Invoked after outputting a message for ":echowindow".
+ */
+    void
+end_echowindow(void)
+{
+    // show the message window now
+    redraw_cmd(FALSE);
+
+    // do not overwrite messages
+    // TODO: only for message window
+    msg_didout = TRUE;
+    if (msg_col == 0)
+	msg_col = 1;
+    in_echowindow = FALSE;
+}
 #endif
 
 /*
diff --git a/src/proto/ex_docmd.pro b/src/proto/ex_docmd.pro
index 509dc11c5d..894b6dae38 100644
--- a/src/proto/ex_docmd.pro
+++ b/src/proto/ex_docmd.pro
@@ -56,6 +56,7 @@ void ex_cd(exarg_T *eap);
 void do_sleep(long msec, int hide_cursor);
 void ex_may_print(exarg_T *eap);
 void ex_redraw(exarg_T *eap);
+void redraw_cmd(int clear);
 int vim_mkdir_emsg(char_u *name, int prot);
 FILE *open_exfile(char_u *fname, int forceit, char *mode);
 void update_topline_cursor(void);
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index dcc14de091..12be54f1f8 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -67,6 +67,8 @@ win_T *popup_get_message_win(void);
 void popup_show_message_win(void);
 int popup_message_win_visible(void);
 void popup_hide_message_win(void);
+void start_echowindow(void);
+void end_echowindow(void);
 int popup_win_closed(win_T *win);
 void popup_set_title(win_T *wp);
 void popup_update_preview_title(void);
diff --git a/src/proto/typval.pro b/src/proto/typval.pro
index 154b668b1e..7d32a03d94 100644
--- a/src/proto/typval.pro
+++ b/src/proto/typval.pro
@@ -20,6 +20,7 @@ int check_for_bool_arg(typval_T *args, int idx);
 int check_for_opt_bool_arg(typval_T *args, int idx);
 int check_for_blob_arg(typval_T *args, int idx);
 int check_for_list_arg(typval_T *args, int idx);
+int check_for_nonnull_list_arg(typval_T *args, int idx);
 int check_for_opt_list_arg(typval_T *args, int idx);
 int check_for_dict_arg(typval_T *args, int idx);
 int check_for_nonnull_dict_arg(typval_T *args, int idx);
diff --git a/src/sign.c b/src/sign.c
index e0264ccb1b..eaefd5f063 100644
--- a/src/sign.c
+++ b/src/sign.c
@@ -2660,11 +2660,8 @@ f_sign_placelist(typval_T *argvars, typval_T *rettv)
     if (in_vim9script() && check_for_list_arg(argvars, 0) == FAIL)
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_list_required));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
 
     // Process the List of sign attributes
     FOR_ALL_LIST_ITEMS(argvars[0].vval.v_list, li)
@@ -2888,11 +2885,8 @@ f_sign_unplacelist(typval_T *argvars, typval_T *rettv)
     if (in_vim9script() && check_for_list_arg(argvars, 0) == FAIL)
 	return;
 
-    if (argvars[0].v_type != VAR_LIST)
-    {
-	emsg(_(e_list_required));
+    if (check_for_list_arg(argvars, 0) == FAIL)
 	return;
-    }
 
     FOR_ALL_LIST_ITEMS(argvars[0].vval.v_list, li)
     {
diff --git a/src/terminal.c b/src/terminal.c
index cc38a1abd5..b4f5e69a26 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -6467,11 +6467,9 @@ f_term_setansicolors(typval_T *argvars, typval_T *rettv UNUSED)
     if (term->tl_vterm == NULL)
 	return;
 
-    if (argvars[1].v_type != VAR_LIST || argvars[1].vval.v_list == NULL)
-    {
-	emsg(_(e_list_required));
+    if (check_for_nonnull_list_arg(argvars, 1) == FAIL)
 	return;
-    }
+
     if (argvars[1].vval.v_list->lv_first == &range_list_item
 	    || argvars[1].vval.v_list->lv_len != 16)
     {
diff --git a/src/testdir/dumps/Test_echowindow_2.dump b/src/testdir/dumps/Test_echowindow_2.dump
index f8bea0c4ad..58b2f3fbf1 100644
--- a/src/testdir/dumps/Test_echowindow_2.dump
+++ b/src/testdir/dumps/Test_echowindow_2.dump
@@ -5,4 +5,4 @@
 |═+0#e000002&@74
 |f|i|r|s|t| |l|i|n|e| @64
 |s|e|c|o|n|d| |l|i|n|e| @63
-| +0#0000000&@56|1|,|1| @10|A|l@1| 
+|:+0#0000000&|c|a|l@1| |S|h|o|w|M|e|s@1|a|g|e|(|'|s|e|c|o|n|d| |l|i|n|e|'|)| @24|1|,|1| @10|A|l@1| 
diff --git a/src/testdir/dumps/Test_echowindow_4.dump b/src/testdir/dumps/Test_echowindow_4.dump
new file mode 100644
index 0000000000..c8bd387c72
--- /dev/null
+++ b/src/testdir/dumps/Test_echowindow_4.dump
@@ -0,0 +1,8 @@
+>═+0#e000002#ffffff0@74
+|l|i|n|e| |1|4| @67
+|l|i|n|e| |1|5| @67
+|l|i|n|e| |1|6| @67
+|l|i|n|e| |1|7| @67
+|l|i|n|e| |1|8| @67
+|l|i|n|e| |1|9| @67
+|:+0#0000000&|c|a|l@1| |M|a|n|y|M|e|s@1|a|g|e|s|(|)| @36|1|,|1| @10|A|l@1| 
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index bb42678acc..0f0ffe878a 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -62,8 +62,8 @@ endfunc
 " Read the port number from the Xportnr file.
 func GetPort()
   let l = []
-  " with 200 it sometimes failed
-  for i in range(400)
+  " with 200 it sometimes failed, with 400 is rarily failed
+  for i in range(600)
     try
       let l = readfile("Xportnr")
     catch
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 95db663bdf..bec0f5fdf8 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -1078,6 +1078,10 @@ func Test_cmdline_complete_various()
   call feedkeys(":all abc\<C-A>\<C-B>\"\<CR>", 'xt')
   call assert_equal("\"all abc\<C-A>", @:)
 
+  " completion for :wincmd with :horizontal modifier
+  call feedkeys(":horizontal wincm\<C-A>\<C-B>\"\<CR>", 'xt')
+  call assert_equal("\"horizontal wincmd", @:)
+
   " completion for a command with a command modifier
   call feedkeys(":topleft new\<C-A>\<C-B>\"\<CR>", 'xt')
   call assert_equal("\"topleft new", @:)
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 18233e7ab1..fbb8d2d2dd 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -1827,6 +1827,44 @@ func Test_sig_file()
   filetype off
 endfunc
 
+" Test dist#ft#FTsil()
+func Test_sil_file()
+  filetype on
+
+  split Xfile.sil
+  call assert_equal('sil', &filetype)
+  bwipe!
+
+  let lines =<< trim END
+  // valid
+  let protoErasedPathA = \ABCProtocol.a
+
+  // also valid
+  let protoErasedPathA =
+          \ABCProtocol.a
+  END
+  call writefile(lines, 'Xfile.sil')
+
+  split Xfile.sil
+  call assert_equal('sil', &filetype)
+  bwipe!
+
+  " SILE
+
+  call writefile(['% some comment'], 'Xfile.sil')
+  split Xfile.sil
+  call assert_equal('sile', &filetype)
+  bwipe!
+
+  call writefile(['\begin[papersize=a6]{document}foo\end{document}'], 'Xfile.sil')
+  split Xfile.sil
+  call assert_equal('sile', &filetype)
+  bwipe!
+
+  call delete('Xfile.sil')
+  filetype off
+endfunc
+
 func Test_inc_file()
   filetype on
 
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 971be40dc4..43eb265d62 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -2244,9 +2244,12 @@ func Test_readdir_sort()
   exe "lang collate" collate
 
   " 5) Errors
-  call assert_fails('call readdir(dir, 1, 1)', 'E715:')
+  call assert_fails('call readdir(dir, 1, 1)', 'E1206:')
   call assert_fails('call readdir(dir, 1, #{sorta: 1})')
+  call assert_fails('call readdir(dir, 1, test_null_dict())', 'E1297:')
+  call assert_fails('call readdirex(dir, 1, 1)', 'E1206:')
   call assert_fails('call readdirex(dir, 1, #{sorta: 1})')
+  call assert_fails('call readdirex(dir, 1, test_null_dict())', 'E1297:')
 
   " 6) ignore other values in dict
   let files = readdir(dir, '1', #{sort: 'c'})
@@ -2285,7 +2288,7 @@ endfunc
 func Test_call()
   call assert_equal(3, call('len', [123]))
   call assert_equal(3, 'len'->call([123]))
-  call assert_fails("call call('len', 123)", 'E714:')
+  call assert_fails("call call('len', 123)", 'E1211:')
   call assert_equal(0, call('', []))
   call assert_equal(0, call('len', test_null_list()))
 
@@ -2580,7 +2583,7 @@ func Test_range()
 
   " list2str()
   call assert_equal('ABC', list2str(range(65, 67)))
-  call assert_fails('let s = list2str(5)', 'E474:')
+  call assert_fails('let s = list2str(5)', 'E1211:')
 
   " lock()
   let thelist = range(5)
diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index e852f00b58..fe6a76b707 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -1217,13 +1217,20 @@ endfunc
 
 " Move the mouse to the top-left in preparation for mouse events
 func PrepareForMouseEvent(args)
-  call extend(a:args, #{row: 1, col:1})
+  call extend(a:args, #{row: 1, col: 1})
   call test_gui_event('mouse', a:args)
+  let g:eventlist = []
   call feedkeys('', 'Lx!')
-  " on MS-Windows the event may have a slight delay
-  if has('win32')
-    sleep 20m
-  endif
+
+  " Wait a bit for the event.  I may not come if the mouse didn't move, wait up
+  " to 100 msec.
+  for n in range(10)
+    if len(g:eventlist) > 0
+      break
+    endif
+    sleep 10m
+  endfor
+  let g:eventlist = []
 endfunc
 
 func MouseWasMoved()
@@ -1236,7 +1243,7 @@ func Test_gui_mouse_move_event()
   CheckNotMacVim
   let args = #{move: 1, button: 0, multiclick: 0, modifiers: 0}
 
-  " by default, does not generate mouse move events
+  " by default, no mouse move events are generated
   set mousemev&
   call assert_false(&mousemev)
 
@@ -1245,7 +1252,6 @@ func Test_gui_mouse_move_event()
 
   " start at mouse pos (1,1), clear counter
   call PrepareForMouseEvent(args)
-  let g:eventlist = []
 
   call extend(args, #{row: 3, col: 30, cell: v:true})
   call test_gui_event('mouse', args)
@@ -1255,13 +1261,12 @@ func Test_gui_mouse_move_event()
   call test_gui_event('mouse', args)
   call feedkeys('', 'Lx!')
 
-  " no events since mousemev off
+  " no events since 'mousemev' is off
   call assert_equal([], g:eventlist)
 
   " turn on mouse events and try the same thing
   set mousemev
   call PrepareForMouseEvent(args)
-  let g:eventlist = []
 
   call extend(args, #{row: 3, col: 30, cell: v:true})
   call test_gui_event('mouse', args)
@@ -1281,7 +1286,6 @@ func Test_gui_mouse_move_event()
   " wiggle the mouse around within a screen cell, shouldn't trigger events
   call extend(args, #{cell: v:false})
   call PrepareForMouseEvent(args)
-  let g:eventlist = []
 
   call extend(args, #{row: 1, col: 2, cell: v:false})
   call test_gui_event('mouse', args)
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index 41998aa0eb..cee6a329f7 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -673,14 +673,14 @@ func Test_complete_func_error()
   func ListColors()
     call complete(col('.'), "blue")
   endfunc
-  call assert_fails('exe "normal i\<C-R>=ListColors()\<CR>"', 'E474:')
+  call assert_fails('exe "normal i\<C-R>=ListColors()\<CR>"', 'E1211:')
   func ListMonths()
     call complete(col('.'), test_null_list())
   endfunc
-  call assert_fails('exe "normal i\<C-R>=ListMonths()\<CR>"', 'E474:')
+  call assert_fails('exe "normal i\<C-R>=ListMonths()\<CR>"', 'E1298:')
   delfunc ListColors
   delfunc ListMonths
-  call assert_fails('call complete_info({})', 'E714:')
+  call assert_fails('call complete_info({})', 'E1211:')
   call assert_equal([], complete_info(['items']).items)
 endfunc
 
diff --git a/src/testdir/test_match.vim b/src/testdir/test_match.vim
index 45f8389757..f654761d64 100644
--- a/src/testdir/test_match.vim
+++ b/src/testdir/test_match.vim
@@ -95,7 +95,7 @@ function Test_match()
   call assert_equal(0, setmatches([]))
   call assert_equal(0, setmatches([{'group': 'MyGroup1', 'pattern': 'TODO', 'priority': 10, 'id': 1}]))
   call clearmatches()
-  call assert_fails('call setmatches(0)', 'E714:')
+  call assert_fails('call setmatches(0)', 'E1211:')
   call assert_fails('call setmatches([0])', 'E474:')
   call assert_fails("call setmatches([{'wrong key': 'wrong value'}])", 'E474:')
   call assert_equal(-1, setmatches([{'group' : 'Search', 'priority' : 10, 'id' : 5, 'pos1' : {}}]))
diff --git a/src/testdir/test_messages.vim b/src/testdir/test_messages.vim
index 6bdaedfd69..10af69c67d 100644
--- a/src/testdir/test_messages.vim
+++ b/src/testdir/test_messages.vim
@@ -396,6 +396,11 @@ func Test_echowindow()
         echowindow a:arg
       endfunc
       echowindow 'first line'
+      func ManyMessages()
+        for n in range(20)
+          echowindow 'line' n
+        endfor
+      endfunc
   END
   call writefile(lines, 'XtestEchowindow')
   let buf = RunVimInTerminal('-S XtestEchowindow', #{rows: 8})
@@ -407,6 +412,9 @@ func Test_echowindow()
   call term_sendkeys(buf, ":call popup_clear()\<CR>")
   call VerifyScreenDump(buf, 'Test_echowindow_3', {})
 
+  call term_sendkeys(buf, ":call ManyMessages()\<CR>")
+  call VerifyScreenDump(buf, 'Test_echowindow_4', {})
+
   " clean up
   call StopVimInTerminal(buf)
   call delete('XtestEchowindow')
diff --git a/src/testdir/test_method.vim b/src/testdir/test_method.vim
index 22a930c5f2..d31cce1876 100644
--- a/src/testdir/test_method.vim
+++ b/src/testdir/test_method.vim
@@ -52,7 +52,7 @@ func Test_dict_method()
   call assert_fails("let x = d->insert(0)", 'E899:')
   call assert_true(d->has_key('two'))
   call assert_equal([['one', 1], ['two', 2], ['three', 3]], d->items())
-  call assert_fails("let x = d->join()", 'E714:')
+  call assert_fails("let x = d->join()", 'E1211:')
   call assert_equal(['one', 'two', 'three'], d->keys())
   call assert_equal(3, d->len())
   call assert_equal(#{one: 2, two: 3, three: 4}, d->map('v:val + 1'))
diff --git a/src/testdir/test_signs.vim b/src/testdir/test_signs.vim
index e23d9ac595..e2387b28c7 100644
--- a/src/testdir/test_signs.vim
+++ b/src/testdir/test_signs.vim
@@ -2010,7 +2010,7 @@ func Test_sign_funcs_multi()
 
   " Invalid arguments
   call assert_equal([], sign_placelist([]))
-  call assert_fails('call sign_placelist({})', "E714:")
+  call assert_fails('call sign_placelist({})', "E1211:")
   call assert_fails('call sign_placelist([[]])', "E715:")
   call assert_fails('call sign_placelist(["abc"])', "E715:")
   call assert_fails('call sign_placelist([100])', "E715:")
@@ -2021,7 +2021,7 @@ func Test_sign_funcs_multi()
 
   " Invalid arguments
   call assert_equal([], []->sign_unplacelist())
-  call assert_fails('call sign_unplacelist({})', "E714:")
+  call assert_fails('call sign_unplacelist({})', "E1211:")
   call assert_fails('call sign_unplacelist([[]])', "E715:")
   call assert_fails('call sign_unplacelist(["abc"])', "E715:")
   call assert_fails('call sign_unplacelist([100])', "E715:")
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index 7d19aa57ee..08f7224b1f 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -2070,7 +2070,7 @@ func Test_terminal_ansicolors_func()
 
   let colors[4] = 'Invalid'
   call assert_fails('call term_setansicolors(buf, colors)', 'E254:')
-  call assert_fails('call term_setansicolors(buf, {})', 'E714:')
+  call assert_fails('call term_setansicolors(buf, {})', 'E1211:')
   set tgc&
 
   call StopShellInTerminal(buf)
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 34fa6c93fc..03ae9c97e0 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -381,7 +381,7 @@ func Test_prop_add_list()
   call assert_fails('call prop_add_list(#{type: "one"}, [[2, 2, 2, 2], [3, 20, 3, 22]])', 'E964:')
   call assert_fails('eval #{type: "one"}->prop_add_list([[2, 2, 2, 2], [3, 20, 3, 22]])', 'E964:')
   call assert_fails('call prop_add_list(test_null_dict(), [[2, 2, 2]])', 'E965:')
-  call assert_fails('call prop_add_list(#{type: "one"}, test_null_list())', 'E714:')
+  call assert_fails('call prop_add_list(#{type: "one"}, test_null_list())', 'E1298:')
   call assert_fails('call prop_add_list(#{type: "one"}, [test_null_list()])', 'E714:')
   call DeletePropTypes()
   bw!
diff --git a/src/testdir/test_usercommands.vim b/src/testdir/test_usercommands.vim
index 9c75a91972..91d8bfd062 100644
--- a/src/testdir/test_usercommands.vim
+++ b/src/testdir/test_usercommands.vim
@@ -103,6 +103,10 @@ function Test_cmdmods()
   call assert_equal('vertical', g:mods)
   vert MyCmd
   call assert_equal('vertical', g:mods)
+  horizontal MyCmd
+  call assert_equal('horizontal', g:mods)
+  hor MyCmd
+  call assert_equal('horizontal', g:mods)
 
   aboveleft belowright botright browse confirm hide keepalt keepjumps
 	      \ keepmarks keeppatterns lockmarks noautocmd noswapfile silent
diff --git a/src/testdir/test_utf8.vim b/src/testdir/test_utf8.vim
index 862e73b9ab..bb99cb3e60 100644
--- a/src/testdir/test_utf8.vim
+++ b/src/testdir/test_utf8.vim
@@ -168,7 +168,7 @@ func Test_setcellwidths()
 
   call setcellwidths([])
 
-  call assert_fails('call setcellwidths(1)', 'E714:')
+  call assert_fails('call setcellwidths(1)', 'E1211:')
 
   call assert_fails('call setcellwidths([1, 2, 0])', 'E1109:')
 
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index be40088d3b..12be156483 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -2274,6 +2274,8 @@ def s:Echomsg()
   echomsg 'some' 'message'
   echoconsole 'nothing'
   echoerr 'went' .. 'wrong'
+  var local = 'window'
+  echowin 'in' local
 enddef
 
 def Test_disassemble_echomsg()
@@ -2289,7 +2291,14 @@ def Test_disassemble_echomsg()
         "echoerr 'went' .. 'wrong'\\_s*" ..
         '\d PUSHS "wentwrong"\_s*' ..
         '\d ECHOERR 1\_s*' ..
-        '\d RETURN void',
+        "var local = 'window'\\_s*" ..
+        '\d\+ PUSHS "window"\_s*' ..
+        '\d\+ STORE $0\_s*' ..
+        "echowin 'in' local\\_s*" ..
+        '\d\+ PUSHS "in"\_s*' ..
+        '\d\+ LOAD $0\_s*' ..
+        '\d\+ ECHOWINDOW 2\_s*' ..
+        '\d\+ RETURN void',
         res)
 enddef
 
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 5aec8ffc86..bdefc8756a 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2011,6 +2011,13 @@ def Test_echoconsole_cmd()
   # output goes anywhere
 enddef
 
+def Test_echowindow_cmd()
+  var local = 'local'
+  echowindow 'something' local # comment
+  # output goes in message window
+  popup_clear()
+enddef
+
 def Test_for_outside_of_function()
   var lines =<< trim END
     vim9script
diff --git a/src/textprop.c b/src/textprop.c
index de3344f89c..5f5c6a2aa2 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -348,11 +348,8 @@ f_prop_add_list(typval_T *argvars, typval_T *rettv UNUSED)
 	    || check_for_list_arg(argvars, 1) == FAIL)
 	return;
 
-    if (argvars[1].vval.v_list == NULL)
-    {
-	emsg(_(e_list_required));
+    if (check_for_nonnull_list_arg(argvars, 1) == FAIL)
 	return;
-    }
 
     dict = argvars[0].vval.v_dict;
     if (dict == NULL || !dict_has_key(dict, "type"))
diff --git a/src/typval.c b/src/typval.c
index 101f48f34a..12a741ec22 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -508,6 +508,23 @@ check_for_list_arg(typval_T *args, int idx)
     return OK;
 }
 
+/*
+ * Give an error and return FAIL unless "args[idx]" is a non-NULL list.
+ */
+    int
+check_for_nonnull_list_arg(typval_T *args, int idx)
+{
+    if (check_for_list_arg(args, idx) == FAIL)
+	return FAIL;
+
+    if (args[idx].vval.v_list == NULL)
+    {
+	semsg(_(e_non_null_list_required_for_argument_nr), idx + 1);
+	return FAIL;
+    }
+    return OK;
+}
+
 /*
  * Check for an optional list argument at 'idx'
  */
diff --git a/src/usercmd.c b/src/usercmd.c
index 71135119e8..6b3eadc934 100644
--- a/src/usercmd.c
+++ b/src/usercmd.c
@@ -1443,6 +1443,9 @@ add_win_cmd_modifers(char_u *buf, cmdmod_T *cmod, int *multi_mods)
     // :vertical
     if (cmod->cmod_split & WSP_VERT)
 	result += add_cmd_modifier(buf, "vertical", multi_mods);
+    // :horizontal
+    if (cmod->cmod_split & WSP_HOR)
+	result += add_cmd_modifier(buf, "horizontal", multi_mods);
     return result;
 }
 
diff --git a/src/version.c b/src/version.c
index c8d711f8b7..841ecba1ce 100644
--- a/src/version.c
+++ b/src/version.c
@@ -722,6 +722,28 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    354,
+/**/
+    353,
+/**/
+    352,
+/**/
+    351,
+/**/
+    350,
+/**/
+    349,
+/**/
+    348,
+/**/
+    347,
+/**/
+    346,
+/**/
+    345,
+/**/
+    344,
 /**/
     343,
 /**/
diff --git a/src/vim9.h b/src/vim9.h
index 3ab1c5aa96..b32dbeab44 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -25,6 +25,7 @@ typedef enum {
     ISN_EXECUTE,    // :execute with isn_arg.number items on top of stack
     ISN_ECHOMSG,    // :echomsg with isn_arg.number items on top of stack
     ISN_ECHOCONSOLE, // :echoconsole with isn_arg.number items on top of stack
+    ISN_ECHOWINDOW, // :echowindow with isn_arg.number items on top of stack
     ISN_ECHOERR,    // :echoerr with isn_arg.number items on top of stack
     ISN_RANGE,	    // compute range from isn_arg.string, push to stack
     ISN_SUBSTITUTE, // :s command with expression
diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index 93032d6bf1..4ad87bc264 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -1735,6 +1735,10 @@ compile_mult_expr(char_u *arg, int cmdidx, cctx_T *cctx)
 	    generate_MULT_EXPR(cctx, ISN_EXECUTE, count);
 	else if (cmdidx == CMD_echomsg)
 	    generate_MULT_EXPR(cctx, ISN_ECHOMSG, count);
+#ifdef HAS_MESSAGE_WINDOW
+	else if (cmdidx == CMD_echowindow)
+	    generate_MULT_EXPR(cctx, ISN_ECHOWINDOW, count);
+#endif
 	else if (cmdidx == CMD_echoconsole)
 	    generate_MULT_EXPR(cctx, ISN_ECHOCONSOLE, count);
 	else
diff --git a/src/vim9compile.c b/src/vim9compile.c
index bf7390b6fa..20366752cf 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -3251,10 +3251,13 @@ compile_def_function(
 
 	    case CMD_echo:
 	    case CMD_echon:
-	    case CMD_execute:
-	    case CMD_echomsg:
-	    case CMD_echoerr:
 	    case CMD_echoconsole:
+	    case CMD_echoerr:
+	    case CMD_echomsg:
+#ifdef HAS_MESSAGE_WINDOW
+	    case CMD_echowindow:
+#endif
+	    case CMD_execute:
 		    line = compile_mult_expr(p, ea.cmdidx, &cctx);
 		    break;
 
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 2f94f05c54..a1311ee177 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -2858,10 +2858,12 @@ exec_instructions(ectx_T *ectx)
 
 	    // :execute {string} ...
 	    // :echomsg {string} ...
+	    // :echowindow {string} ...
 	    // :echoconsole {string} ...
 	    // :echoerr {string} ...
 	    case ISN_EXECUTE:
 	    case ISN_ECHOMSG:
+	    case ISN_ECHOWINDOW:
 	    case ISN_ECHOCONSOLE:
 	    case ISN_ECHOERR:
 		{
@@ -2932,6 +2934,14 @@ exec_instructions(ectx_T *ectx)
 				msg_attr(ga.ga_data, echo_attr);
 				out_flush();
 			    }
+#ifdef HAS_MESSAGE_WINDOW
+			    else if (iptr->isn_type == ISN_ECHOWINDOW)
+			    {
+				start_echowindow();
+				msg_attr(ga.ga_data, echo_attr);
+				end_echowindow();
+			    }
+#endif
 			    else if (iptr->isn_type == ISN_ECHOCONSOLE)
 			    {
 				ui_write(ga.ga_data, (int)STRLEN(ga.ga_data),
@@ -5570,6 +5580,10 @@ list_instructions(char *pfx, isn_T *instr, int instr_count, ufunc_T *ufunc)
 		smsg("%s%4d ECHOMSG %lld", pfx, current,
 					  (varnumber_T)(iptr->isn_arg.number));
 		break;
+	    case ISN_ECHOWINDOW:
+		smsg("%s%4d ECHOWINDOW %lld", pfx, current,
+					  (varnumber_T)(iptr->isn_arg.number));
+		break;
 	    case ISN_ECHOCONSOLE:
 		smsg("%s%4d ECHOCONSOLE %lld", pfx, current,
 					  (varnumber_T)(iptr->isn_arg.number));
diff --git a/src/vim9instr.c b/src/vim9instr.c
index f20d993728..a13516bbb2 100644
--- a/src/vim9instr.c
+++ b/src/vim9instr.c
@@ -2245,6 +2245,7 @@ delete_instr(isn_T *isn)
 	case ISN_ECHOCONSOLE:
 	case ISN_ECHOERR:
 	case ISN_ECHOMSG:
+	case ISN_ECHOWINDOW:
 	case ISN_ENDTRY:
 	case ISN_EXECCONCAT:
 	case ISN_EXECUTE: