diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 8666a252f..79ef1180d 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -614,6 +614,7 @@ static void do_timer(CFRunLoopTimerRef timer, void* data)
 - (BOOL)windowShouldClose:(FLWindow *)w;
 - (BOOL)containsGLsubwindow;
 - (void)setContainsGLsubwindow:(BOOL)contains;
+- (BOOL)canBecomeKeyWindow;
 @end
 
 @implementation FLWindow
@@ -650,6 +651,16 @@ static void do_timer(CFRunLoopTimerRef timer, void* data)
 {
   containsGLsubwindow = contains;
 }
+- (BOOL)canBecomeKeyWindow
+{
+  // before 10.5, the default impl of canBecomeKeyWindow is not OK for tooltip windows
+  // we return YES for these windows
+  BOOL retval;
+  Fl_Window *flw = (Fl_Window*)[self getFl_Window];
+  if(fl_mac_os_version < 0x1050 && flw->tooltip_window()) retval = YES;
+  else retval = [super canBecomeKeyWindow];
+  return retval;
+}
 @end
 
 /*