diff --git a/qmake/library/proitems.cpp b/qmake/library/proitems.cpp
index 8bbde9f8c0a..41bed69f00a 100644
--- a/qmake/library/proitems.cpp
+++ b/qmake/library/proitems.cpp
@@ -517,4 +517,9 @@ ProKey ProFile::getHashStr(const ushort *&tPtr)
     return ret;
 }
 
+QDebug operator<<(QDebug debug, const ProString &str)
+{
+    return debug << str.toQString();
+}
+
 QT_END_NAMESPACE
diff --git a/qmake/library/proitems.h b/qmake/library/proitems.h
index 71e5e053671..0e0bebddc7c 100644
--- a/qmake/library/proitems.h
+++ b/qmake/library/proitems.h
@@ -31,6 +31,7 @@
 
 #include "qmake_global.h"
 
+#include <qdebug.h>
 #include <qstring.h>
 #include <qvector.h>
 #include <qhash.h>
@@ -468,6 +469,8 @@ struct ProFunctionDefs {
     QHash<ProKey, ProFunctionDef> replaceFunctions;
 };
 
+QDebug operator<<(QDebug debug, const ProString &str);
+
 QT_END_NAMESPACE
 
 #endif // PROITEMS_H