diff --git a/src/plugins/coreplugin/fileutils.h b/src/plugins/coreplugin/fileutils.h
index a23b5a8e79b..5050a770762 100644
--- a/src/plugins/coreplugin/fileutils.h
+++ b/src/plugins/coreplugin/fileutils.h
@@ -35,10 +35,11 @@
 
 #include "coreplugin/core_global.h"
 
+QT_BEGIN_NAMESPACE
 class QWidget;
+QT_END_NAMESPACE
 
 namespace Core {
-
 namespace Internal {
 
 struct CORE_EXPORT FileUtils