diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index af69a91e4a..d5574a4dd1 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -36,6 +36,7 @@
 
 #ifndef QOBJECTDEFS_H
 #error Do not include qobjectdefs_impl.h directly
+#include <QtCore/qnamespace.h>
 #endif
 
 #if 0