diff --git a/MASPreferencesWindowController.h b/MASPreferencesWindowController.h
index 02bcdaf..275f5d1 100644
--- a/MASPreferencesWindowController.h
+++ b/MASPreferencesWindowController.h
@@ -23,7 +23,7 @@ __attribute__((__visibility__("default")))
     NSMutableDictionary *_minimumViewRects;
     NSString *_title;
     NSViewController <MASPreferencesViewController> *_selectedViewController;
-	NSToolbar *_toolbar;
+    NSToolbar * __unsafe_unretained _toolbar;
 }
 
 @property (nonatomic, readonly) NSMutableArray *viewControllers;