gistfile1

diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 228ef9d..f64655f 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -522,6 +522,17 @@ void QCocoaWindow::setWindowFlags(Qt::WindowFlags flags)
         if (!(styleMask & NSBorderlessWindowMask)) {
             setWindowTitle(window()->title());
         }
+
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+        if (QSysInfo::QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7) {
+            NSWindowCollectionBehavior behavior = [m_nsWindow collectionBehavior];
+            if (flags & Qt::WindowFullscreenButtonHint)
+                behavior |= NSWindowCollectionBehaviorFullScreenPrimary;
+            else
+                behavior &= ~NSWindowCollectionBehaviorFullScreenPrimary;
+            [m_nsWindow setCollectionBehavior:behavior];
+        }
+#endif
     }
 
     m_windowFlags = flags;