diff --git a/src/kontactplugin/korganizer/kcmapptsummary.cpp b/src/kontactplugin/korganizer/kcmapptsummary.cpp
--- a/src/kontactplugin/korganizer/kcmapptsummary.cpp
+++ b/src/kontactplugin/korganizer/kcmapptsummary.cpp
@@ -30,6 +30,8 @@
 #include <KLocalizedString>
 #include <KConfig>
 
+#include <QButtonGroup>
+
 KCModule *create_apptsummary(QWidget *parent, const char *)
 {
     return new KCMApptSummary(parent);