diff --git a/src/plugins/platforms/wayland/qwaylandscreen.cpp b/src/plugins/platforms/wayland/qwaylandscreen.cpp
index 943e29a05c1..88667ae0d4f 100644
--- a/src/plugins/platforms/wayland/qwaylandscreen.cpp
+++ b/src/plugins/platforms/wayland/qwaylandscreen.cpp
@@ -97,7 +97,7 @@ QImage::Format QWaylandScreen::format() const
 
 QSizeF QWaylandScreen::physicalSize() const
 {
-    if (mPhysicalSize.isNull())
+    if (mPhysicalSize.isEmpty())
         return QPlatformScreen::physicalSize();
     else
         return mPhysicalSize;