diff --git a/hw/xquartz/X11Application.m b/hw/xquartz/X11Application.m
index 10afdf91a43cca833e4e3f5537e350c748e921a3..a009d6415ace521a98c8254e7973bb69ba7f49b4 100644
--- a/hw/xquartz/X11Application.m
+++ b/hw/xquartz/X11Application.m
@@ -1082,12 +1082,15 @@ X11ApplicationCanEnterRandR(void)
     if (!XQuartzIsRootless)
         QuartzShowFullscreen(FALSE);
 
-    switch (NSRunAlertPanel(title, @"%@",
-                            NSLocalizedString(@"Allow",
-                                              @""),
-                            NSLocalizedString(@"Cancel",
-                                              @""),
-                            NSLocalizedString(@"Always Allow", @""), msg)) {
+    NSInteger __block alert_result;
+    dispatch_sync(dispatch_get_main_queue(), ^{
+        alert_result = NSRunAlertPanel(title, @"%@",
+                                       NSLocalizedString(@"Allow", @""),
+                                       NSLocalizedString(@"Cancel", @""),
+                                       NSLocalizedString(@"Always Allow", @""), msg);
+    });
+
+    switch (alert_result) {
     case NSAlertOtherReturn:
         [X11App prefs_set_boolean:@PREFS_NO_RANDR_ALERT value:YES];
         [X11App prefs_synchronize];