diff --git a/src/libs/utils/mimetypes/mimedatabase_p.h b/src/libs/utils/mimetypes/mimedatabase_p.h
index 2693846380d..7eea3515ebf 100644
--- a/src/libs/utils/mimetypes/mimedatabase_p.h
+++ b/src/libs/utils/mimetypes/mimedatabase_p.h
@@ -47,6 +47,9 @@
 
 #include <QtCore/qhash.h>
 #include <QtCore/qmutex.h>
+QT_BEGIN_NAMESPACE
+class QIODevice;
+QT_END_NAMESPACE
 
 #include "mimetype.h"
 #include "mimetype_p.h"