diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index aaaf530..52282cb 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -1466,7 +1466,7 @@
 	$(MAKE) /NOLOGO -f Make_dos.mak
 	cd ..
 
-testgvim:
+testgvim testgui:
 	cd testdir
 	$(MAKE) /NOLOGO -f Make_dos.mak VIMPROG=..\gvim
 	cd ..
diff --git a/src/gui.c b/src/gui.c
index 3b0ebac..68c64d2 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -5641,3 +5641,26 @@
     return NUL;
 }
 
+/*
+ * If the "--gui-log-file fname" argument is given write the dialog title and
+ * message to a file and return TRUE.  Otherwise return FALSE.
+ * When there is any problem opening the file or writing to the file this is
+ * ignored, showing the dialog might get the test to get stuck.
+ */
+    int
+gui_dialog_log(char_u *title, char_u *message)
+{
+    char_u  *fname = get_gui_dialog_file();
+    FILE    *fd;
+
+    if (fname == NULL)
+	return FALSE;
+
+    fd = mch_fopen((char *)fname, "a");
+    if (fd != NULL)
+    {
+	fprintf(fd, "%s: %s\n", title, message);
+	fclose(fd);
+    }
+    return TRUE;
+}
diff --git a/src/main.c b/src/main.c
index b92be4c..3d86796 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1025,6 +1025,17 @@
 	;
 }
 
+#if defined(FEAT_GUI) || defined(PROTO)
+/*
+ * If a --gui-dialog-file argument was given return the file name.
+ * Otherwise return NULL.
+ */
+    char_u *
+get_gui_dialog_file(void)
+{
+    return params.gui_dialog_file;
+}
+#endif
 
 // When TRUE in a safe state when starting to wait for a character.
 static int	was_safe = FALSE;
@@ -2009,6 +2020,7 @@
 				// "--log fname" start logging early
 				// "--nofork" don't fork
 				// "--not-a-term" don't warn for not a term
+				// "--gui-dialog-file fname" write dialog text
 				// "--ttyfail" exit if not a term
 				// "--noplugin[s]" skip plugins
 				// "--cmd <cmd>" execute cmd before vimrc
@@ -2052,6 +2064,12 @@
 		    p_lpl = FALSE;
 		else if (STRNICMP(argv[0] + argv_idx, "not-a-term", 10) == 0)
 		    parmp->not_a_term = TRUE;
+		else if (STRNICMP(argv[0] + argv_idx, "gui-dialog-file", 15)
+									 == 0)
+		{
+		    want_argument = TRUE;
+		    argv_idx += 15;
+		}
 		else if (STRNICMP(argv[0] + argv_idx, "ttyfail", 7) == 0)
 		    parmp->tty_fail = TRUE;
 		else if (STRNICMP(argv[0] + argv_idx, "cmd", 3) == 0)
@@ -2448,6 +2466,15 @@
 			parmp->pre_commands[parmp->n_pre_commands++] =
 							    (char_u *)argv[0];
 		    }
+		    // --gui-dialog-file fname
+		    if (argv[-1][2] == 'g')
+		    {
+			// without GUI ignore the argument
+#ifdef FEAT_GUI
+			parmp->gui_dialog_file = (char_u *)argv[0];
+#endif
+		    }
+
 		    // "--startuptime <file>" already handled
 		    // "--log <file>" already handled
 		    break;
@@ -3515,6 +3542,9 @@
 #endif
     main_msg(_("-T <terminal>\tSet terminal type to <terminal>"));
     main_msg(_("--not-a-term\t\tSkip warning for input/output not being a terminal"));
+#ifdef FEAT_GUI
+    main_msg(_("--gui-dialog-file {fname}  For testing: write dialog text"));
+#endif
     main_msg(_("--ttyfail\t\tExit if input or output is not a terminal"));
     main_msg(_("-u <vimrc>\t\tUse <vimrc> instead of any .vimrc"));
 #ifdef FEAT_GUI
diff --git a/src/message.c b/src/message.c
index ed9b532..3c9e4a0 100644
--- a/src/message.c
+++ b/src/message.c
@@ -3798,7 +3798,11 @@
     // When GUI is running and 'c' not in 'guioptions', use the GUI dialog
     if (gui.in_use && vim_strchr(p_go, GO_CONDIALOG) == NULL)
     {
-	c = gui_mch_dialog(type, title, message, buttons, dfltbutton,
+	// --gui-dialog-file: write text to a file
+	if (gui_dialog_log(title, message))
+	    c = dfltbutton;
+	else
+	    c = gui_mch_dialog(type, title, message, buttons, dfltbutton,
 							   textfield, ex_cmd);
 	// avoid a hit-enter prompt without clearing the cmdline
 	need_wait_return = FALSE;
diff --git a/src/os_mswin.c b/src/os_mswin.c
index b6e8d71..48a6972 100644
--- a/src/os_mswin.c
+++ b/src/os_mswin.c
@@ -676,7 +676,10 @@
 	    for (p = (char *)error_ga.ga_data; *p; ++p)
 		if (!isspace(*p))
 		{
-		    (void)gui_mch_dialog(
+		    // Only use a dialog when not using --gui-dialog-file:
+		    // write text to a file.
+		    if (!gui_dialog_log((char_u *)"Errors", p))
+			(void)gui_mch_dialog(
 				     gui.starting ? VIM_INFO :
 					     VIM_ERROR,
 				     gui.starting ? (char_u *)_("Message") :
diff --git a/src/proto/gui.pro b/src/proto/gui.pro
index 209e7f1..2a0ac80 100644
--- a/src/proto/gui.pro
+++ b/src/proto/gui.pro
@@ -67,4 +67,5 @@
 int gui_do_findrepl(int flags, char_u *find_text, char_u *repl_text, int down);
 void gui_handle_drop(int x, int y, int_u modifiers, char_u **fnames, int count);
 int check_for_interrupt(int key, int modifiers_arg);
+int gui_dialog_log(char_u *title, char_u *message);
 /* vim: set ft=c : */
diff --git a/src/proto/main.pro b/src/proto/main.pro
index ff3e1a5..4368e24 100644
--- a/src/proto/main.pro
+++ b/src/proto/main.pro
@@ -2,6 +2,7 @@
 int vim_main2(void);
 void common_init(mparm_T *paramp);
 int is_not_a_term(void);
+char_u *get_gui_dialog_file(void);
 int op_pending(void);
 void may_trigger_safestate(int safe);
 void state_no_longer_safe(char *reason);
diff --git a/src/structs.h b/src/structs.h
index 58152b9..7fe97fd 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -4207,6 +4207,9 @@
 
     int		want_full_screen;
     int		not_a_term;		// no warning for missing term?
+#ifdef FEAT_GUI
+    char_u	*gui_dialog_file;	// file to write dialog text in
+#endif
     int		tty_fail;		// exit if not a tty
     char_u	*term;			// specified terminal name
 #ifdef FEAT_CRYPT
diff --git a/src/testdir/Make_dos.mak b/src/testdir/Make_dos.mak
index 8956384..9d1dc4e 100644
--- a/src/testdir/Make_dos.mak
+++ b/src/testdir/Make_dos.mak
@@ -19,6 +19,9 @@
 
 .SUFFIXES: .in .out .res .vim
 
+# Add --gui-dialog-file to avoid getting stuck in a dialog.
+COMMON_ARGS = $(NO_INITS) --gui-dialog-file guidialog
+
 nongui:	nolog tinytests newtests report
 
 gui:	nolog tinytests newtests report
@@ -31,7 +34,7 @@
 	@rem without the +eval feature test_result.log is a copy of test.log
 	@if exist test.log ( copy /y test.log test_result.log > nul ) \
 		else ( echo No failures reported > test_result.log )
-	$(VIMPROG) -u NONE $(NO_INITS) -S summarize.vim messages
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S summarize.vim messages
 	@echo.
 	@echo Test results:
 	@cmd /c type test_result.log
@@ -70,6 +73,8 @@
 	-if exist messages del messages
 	-if exist benchmark.out del benchmark.out
 	-if exist opt_test.vim del opt_test.vim
+	-if exist guidialog del guidialog
+	-if exist guidialogfile del guidialogfile
 
 nolog:
 	-if exist test.log del test.log
@@ -84,7 +89,7 @@
 $(DOSTMP_INFILES): $(*B).in
 	if not exist $(DOSTMP)\NUL md $(DOSTMP)
 	if exist $@ del $@
-	$(VIMPROG) -u dos.vim $(NO_INITS) "+set ff=dos|f $@|wq" $(*B).in
+	$(VIMPROG) -u dos.vim $(COMMON_ARGS) "+set ff=dos|f $@|wq" $(*B).in
 
 # For each input file dostmp/test99.in run the tests.
 # This moves test99.in to test99.in.bak temporarily.
@@ -94,7 +99,7 @@
 	move $(*B).in $(*B).in.bak > nul
 	copy $(DOSTMP)\$(*B).in $(*B).in > nul
 	copy $(*B).ok test.ok > nul
-	$(VIMPROG) -u dos.vim $(NO_INITS) -s dotest.in $(*B).in
+	$(VIMPROG) -u dos.vim $(COMMON_ARGS) -s dotest.in $(*B).in
 	-@if exist test.out MOVE /y test.out $(DOSTMP)\$(*B).out > nul
 	-@if exist $(*B).in.bak move /y $(*B).in.bak $(*B).in > nul
 	-@if exist test.ok del test.ok
@@ -103,7 +108,7 @@
 	-@if exist XfakeHOME rd /s /q XfakeHOME
 	-@del X*
 	-@if exist viminfo del viminfo
-	$(VIMPROG) -u dos.vim $(NO_INITS) "+set ff=unix|f test.out|wq" \
+	$(VIMPROG) -u dos.vim $(COMMON_ARGS) "+set ff=unix|f test.out|wq" \
 		$(DOSTMP)\$(*B).out
 	@diff test.out $*.ok & if errorlevel 1 \
 		( move /y test.out $*.failed > nul \
@@ -123,12 +128,12 @@
 
 .vim.res:
 	@echo $(VIMPROG) > vimcmd
-	$(VIMPROG) -u NONE $(NO_INITS) -S runtest.vim $*.vim
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S runtest.vim $*.vim
 	@del vimcmd
 
 test_gui.res: test_gui.vim
 	@echo $(VIMPROG) > vimcmd
-	$(VIMPROG) -u NONE $(NO_INITS) -S runtest.vim $*.vim
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S runtest.vim $*.vim
 	@del vimcmd
 
 test_gui_init.res: test_gui_init.vim
@@ -142,6 +147,6 @@
 test_bench_regexp.res: test_bench_regexp.vim
 	-if exist benchmark.out del benchmark.out
 	@echo $(VIMPROG) > vimcmd
-	$(VIMPROG) -u NONE $(NO_INITS) -S runtest.vim $*.vim
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S runtest.vim $*.vim
 	@del vimcmd
 	@IF EXIST benchmark.out ( type benchmark.out )
diff --git a/src/testdir/Make_ming.mak b/src/testdir/Make_ming.mak
index 5e17963..0638ade 100644
--- a/src/testdir/Make_ming.mak
+++ b/src/testdir/Make_ming.mak
@@ -31,6 +31,9 @@
 
 .SUFFIXES: .in .out .res .vim
 
+# Add --gui-dialog-file to avoid getting stuck in a dialog.
+COMMON_ARGS = $(NO_INITS) --gui-dialog-file guidialog
+
 nongui:	nolog tinytests newtests report
 
 gui:	nolog tinytests newtests report
@@ -43,7 +46,7 @@
 	@rem without the +eval feature test_result.log is a copy of test.log
 	@if exist test.log ( copy /y test.log test_result.log > nul ) \
 		else ( echo No failures reported > test_result.log )
-	$(VIMPROG) -u NONE $(NO_INITS) -S summarize.vim messages
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S summarize.vim messages
 	@echo.
 	@echo Test results:
 	@cmd /c type test_result.log
@@ -82,6 +85,8 @@
 	-@if exist messages $(DEL) messages
 	-@if exist benchmark.out del benchmark.out
 	-@if exist opt_test.vim $(DEL) opt_test.vim
+	-@if exist guidialog $(DEL) guidialog
+	-@if exist guidialogfile $(DEL) guidialogfile
 
 nolog:
 	-@if exist test.log $(DEL) test.log
@@ -96,7 +101,7 @@
 $(DOSTMP)/%.in : %.in
 	if not exist $(DOSTMP)\nul mkdir $(DOSTMP)
 	if exist $(DOSTMP)\$< $(DEL) $(DOSTMP)\$<
-	$(VIMPROG) -u dos.vim $(NO_INITS) "+set ff=dos|f $@|wq" $<
+	$(VIMPROG) -u dos.vim $(COMMON_ARGS) "+set ff=dos|f $@|wq" $<
 
 # For each input file dostmp/test99.in run the tests.
 # This moves test99.in to test99.in.bak temporarily.
@@ -106,7 +111,7 @@
 	$(MV) $(notdir $<) $(notdir $<).bak > NUL
 	$(CP) $(DOSTMP)\$(notdir $<) $(notdir $<) > NUL
 	$(CP) $(basename $@).ok test.ok > NUL
-	$(VIMPROG) -u dos.vim $(NO_INITS) -s dotest.in $(notdir $<)
+	$(VIMPROG) -u dos.vim $(COMMON_ARGS) -s dotest.in $(notdir $<)
 	-@if exist test.out $(MV) test.out $(DOSTMP)\$@ > NUL
 	-@if exist $(notdir $<).bak $(MV) $(notdir $<).bak $(notdir $<) > NUL
 	-@if exist test.ok $(DEL) test.ok
@@ -115,7 +120,7 @@
 	-@if exist XfakeHOME $(DELDIR) XfakeHOME
 	-@del X*
 	-@if exist viminfo del viminfo
-	$(VIMPROG) -u dos.vim $(NO_INITS) "+set ff=unix|f test.out|wq" \
+	$(VIMPROG) -u dos.vim $(COMMON_ARGS) "+set ff=unix|f test.out|wq" \
 		$(DOSTMP)\$@
 	@diff test.out $(basename $@).ok & if errorlevel 1 \
 		( $(MV) test.out $(basename $@).failed > NUL \
@@ -135,12 +140,12 @@
 
 .vim.res:
 	@echo $(VIMPROG) > vimcmd
-	$(VIMPROG) -u NONE $(NO_INITS) -S runtest.vim $*.vim
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S runtest.vim $*.vim
 	@$(DEL) vimcmd
 
 test_gui.res: test_gui.vim
 	@echo $(VIMPROG) > vimcmd
-	$(VIMPROG) -u NONE $(NO_INITS) -S runtest.vim $<
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S runtest.vim $<
 	@$(DEL) vimcmd
 
 test_gui_init.res: test_gui_init.vim
@@ -154,6 +159,6 @@
 test_bench_regexp.res: test_bench_regexp.vim
 	-$(DEL) benchmark.out
 	@echo $(VIMPROG) > vimcmd
-	$(VIMPROG) -u NONE $(NO_INITS) -S runtest.vim $*.vim
+	$(VIMPROG) -u NONE $(COMMON_ARGS) -S runtest.vim $*.vim
 	@$(DEL) vimcmd
 	$(CAT) benchmark.out
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index c782da9..adec1f1 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -89,6 +89,7 @@
 	-rm -rf $(RM_ON_RUN) $(RM_ON_START)
 	-rm -f valgrind.*
 	-rm -f asan.*
+	-rm -f guidialog guidialogfile
 
 # Delete the files produced by benchmarking, so they can run again.
 benchmarkclean:
@@ -127,7 +128,8 @@
 # New style of tests uses Vim script with assert calls.  These are easier
 # to write and a lot easier to read and debug.
 # Limitation: Only works with the +eval feature.
-RUN_VIMTEST = VIMRUNTIME=$(SCRIPTSOURCE) $(VALGRIND) $(VIMPROG) -f $(GUI_FLAG) -u unix.vim
+# Add --gui-dialog-file to avoid getting stuck in a dialog.
+RUN_VIMTEST = VIMRUNTIME=$(SCRIPTSOURCE) $(VALGRIND) $(VIMPROG) -f $(GUI_FLAG) -u unix.vim --gui-dialog-file guidialog
 
 newtests: newtestssilent
 	@/bin/sh -c "if test -f messages; then cat messages; fi"
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 766f983..a4c238e 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -245,6 +245,12 @@
     call popup_clear(1)
   endif
 
+  if filereadable('guidialogfile')
+    call add(v:errors, "Unexpected dialog:")
+    call add(v:errors, readfile('guidialogfile').join('\n'))
+    call delete('guidialogfile')
+  endif
+
   " Close any extra tab pages and windows and make the current one not modified.
   while tabpagenr('$') > 1
     let winid = win_getid()
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index e442a59..60636fd 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -276,6 +276,7 @@
     let cmd = cmd . ' -u ' . name
   endif
   let cmd .= ' --not-a-term'
+  let cmd .= ' --gui-dialog-file guidialogfile'
   let cmd = substitute(cmd, 'VIMRUNTIME=\S\+', '', '')
 
   " If using valgrind, make sure every run uses a different log file.
diff --git a/src/version.c b/src/version.c
index 745f85c..eef7e51 100644
--- a/src/version.c
+++ b/src/version.c
@@ -735,6 +735,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    5084,
+/**/
     5083,
 /**/
     5082,