diff --git a/src/plugins/platforms/cocoa/qnswindowdelegate.mm b/src/plugins/platforms/cocoa/qnswindowdelegate.mm
index a18fe693fa..e5041fb863 100644
--- a/src/plugins/platforms/cocoa/qnswindowdelegate.mm
+++ b/src/plugins/platforms/cocoa/qnswindowdelegate.mm
@@ -88,6 +88,7 @@
 */
 - (NSSize)window:(NSWindow *)window willUseFullScreenContentSize:(NSSize)proposedSize
 {
+    Q_UNUSED(window);
     Q_ASSERT(NSEqualSizes(m_cocoaWindow->screen()->geometry().size().toCGSize(), proposedSize));
     return proposedSize;
 }