diff --git a/runtime/doc/gui_mac.txt b/runtime/doc/gui_mac.txt
index cf731f2e9d..a8df0c07a2 100644
--- a/runtime/doc/gui_mac.txt
+++ b/runtime/doc/gui_mac.txt
@@ -256,6 +256,7 @@ Here is a list of relevant dictionary entries:
 KEY				VALUE ~
 MMCellWidthMultiplier		width of a normal glyph in em units [float]
 MMDialogsTrackPwd		open/save dialogs track the Vim pwd [bool]
+MMFullScreenFadeTime		fade delay for non-native fullscreen [float]
 MMLoginShellArgument		login shell parameter [string]
 MMLoginShellCommand		which shell to use to launch Vim [string]
 MMNoFontSubstitution		disable automatic font substitution [bool]
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 6130cee347..4f5719cf17 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -3456,6 +3456,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 	See 'fuoptions' for how Vim resizes and colors the background when 
 	entering and leaving fullscreen mode.
 
+	You can use the hidden preference MMFullScreenFadeTime to adjust how
+	long the animation takes to fade in and out.  The default is 0.25
+	seconds.  See |macvim-preferences|for how to set hidden preferences.
+
 	Note: Setting 'fullscreen' usually changes the size of the Vim
 	control. However, for technical reasons, 'lines' and 'columns' will
 	currently only be updated when Vim runs its event loop. As a