diff --git a/src/libs/utils/filesearch.cpp b/src/libs/utils/filesearch.cpp
index 877c859be27932c7841c7f822cecf686bfcae2b3..f1fe026cacf230e6a052c85710bc523de49a6267 100644
--- a/src/libs/utils/filesearch.cpp
+++ b/src/libs/utils/filesearch.cpp
@@ -28,6 +28,7 @@
 **************************************************************************/
 
 #include "filesearch.h"
+#include <cctype>
 
 #include <QtCore/QFile>
 #include <QtCore/QDir>