diff --git a/commit.c b/commit.c
index 4385ae4329..f7ea9d9928 100644
--- a/commit.c
+++ b/commit.c
@@ -1637,12 +1637,12 @@ static int find_invalid_utf8(const char *buf, int len)
 }
 
 /*
- * This verifies that the buffer is in proper utf8 format.
+ * This ensures that the buffer is in proper utf8 format.
  *
  * If it isn't, it assumes any non-utf8 characters are Latin1,
  * and does the conversion.
  */
-static int verify_utf8(struct strbuf *buf)
+static int ensure_utf8(struct strbuf *buf)
 {
 	int ok = 1;
 	long pos = 0;
@@ -1726,6 +1726,7 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 	struct repository *r = the_repository;
 	int result = 0;
 	int encoding_is_utf8;
+	bool warned = false;
 	struct strbuf buffer = STRBUF_INIT, compat_buffer = STRBUF_INIT;
 	struct strbuf sig = STRBUF_INIT, compat_sig = STRBUF_INIT;
 	struct object_id *parent_buf = NULL, *compat_oid = NULL;
@@ -1747,6 +1748,13 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 		oidcpy(&parent_buf[i++], &p->item->object.oid);
 
 	write_commit_tree(&buffer, msg, msg_len, tree, parent_buf, nparents, author, committer, extra);
+
+	/* And check the encoding. */
+	if (encoding_is_utf8 && !ensure_utf8(&buffer)) {
+		fprintf(stderr, _(commit_utf8_warn));
+		warned = true;
+	}
+
 	if (sign_commit && sign_buffer(&buffer, &sig, sign_commit,
 				       SIGN_BUFFER_USE_DEFAULT_KEY)) {
 		result = -1;
@@ -1780,6 +1788,9 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 		free_commit_extra_headers(compat_extra);
 		free(mapped_parents);
 
+		if (encoding_is_utf8 && !ensure_utf8(&compat_buffer) && !warned)
+			fprintf(stderr, _(commit_utf8_warn));
+
 		if (sign_commit && sign_buffer(&compat_buffer, &compat_sig,
 					       sign_commit,
 					       SIGN_BUFFER_USE_DEFAULT_KEY)) {
@@ -1818,10 +1829,6 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 		}
 	}
 
-	/* And check the encoding. */
-	if (encoding_is_utf8 && (!verify_utf8(&buffer) || !verify_utf8(&compat_buffer)))
-		fprintf(stderr, _(commit_utf8_warn));
-
 	if (r->compat_hash_algo) {
 		hash_object_file(r->compat_hash_algo, compat_buffer.buf, compat_buffer.len,
 			OBJ_COMMIT, &compat_oid_buf);
diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 1201c85ba6..aa9108da54 100755
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -462,4 +462,14 @@ test_expect_success 'custom `gpg.program`' '
 	git commit -S --allow-empty -m signed-commit
 '
 
+test_expect_success GPG 'commit verifies with non-UTF-8 commit message' '
+	printf "I hate\\376\\377UTF-8\\n" >message &&
+	echo unusual-message >file &&
+	git add file &&
+	test_tick && git commit -S -F message 2>err &&
+	git verify-commit HEAD &&
+	grep "commit message did not conform to UTF-8" err >lines &&
+	test_line_count = 1 lines
+'
+
 test_done