--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -3219,28 +3219,32 @@ static const NSString* kStateTitleKey = 
 static const NSString* kStateDrawsContentsIntoWindowFrameKey = @"drawsContentsIntoWindowFrame";
 static const NSString* kStateActiveTitlebarColorKey = @"activeTitlebarColor";
 static const NSString* kStateInactiveTitlebarColorKey = @"inactiveTitlebarColor";
 static const NSString* kStateShowsToolbarButton = @"showsToolbarButton";
 static const NSString* kStateCollectionBehavior = @"collectionBehavior";
 
 - (void)importState:(NSDictionary*)aState
 {
-  [self setTitle:[aState objectForKey:kStateTitleKey]];
+  if (NSString* title = [aState objectForKey:kStateTitleKey]) {
+    [self setTitle:title];
+  }
   [self setDrawsContentsIntoWindowFrame:[[aState objectForKey:kStateDrawsContentsIntoWindowFrameKey] boolValue]];
   [self setTitlebarColor:[aState objectForKey:kStateActiveTitlebarColorKey] forActiveWindow:YES];
   [self setTitlebarColor:[aState objectForKey:kStateInactiveTitlebarColorKey] forActiveWindow:NO];
   [self setShowsToolbarButton:[[aState objectForKey:kStateShowsToolbarButton] boolValue]];
   [self setCollectionBehavior:[[aState objectForKey:kStateCollectionBehavior] unsignedIntValue]];
 }
 
 - (NSMutableDictionary*)exportState
 {
   NSMutableDictionary* state = [NSMutableDictionary dictionaryWithCapacity:10];
-  [state setObject:[self title] forKey:kStateTitleKey];
+  if (NSString* title = [self title]) {
+    [state setObject:title forKey:kStateTitleKey];
+  }
   [state setObject:[NSNumber numberWithBool:[self drawsContentsIntoWindowFrame]]
             forKey:kStateDrawsContentsIntoWindowFrameKey];
   NSColor* activeTitlebarColor = [self titlebarColorForActiveWindow:YES];
   if (activeTitlebarColor) {
     [state setObject:activeTitlebarColor forKey:kStateActiveTitlebarColorKey];
   }
   NSColor* inactiveTitlebarColor = [self titlebarColorForActiveWindow:NO];
   if (inactiveTitlebarColor) {