diff --git a/rtgui/extprog.h b/rtgui/extprog.h
index 86dbc1674..cdcf14e48 100644
--- a/rtgui/extprog.h
+++ b/rtgui/extprog.h
@@ -20,6 +20,7 @@
 
 #include <vector>
 
+#include <glibmm/refptr.h>
 #include <glibmm/ustring.h>
 
 #include "threadutils.h"