diff --git a/src/ui-knowledge.c b/src/ui-knowledge.c
index 0e29c594..dd3eb1ce 100644
--- a/src/ui-knowledge.c
+++ b/src/ui-knowledge.c
@@ -29,6 +29,7 @@
 #include "store.h"
 #include "ui.h"
 #include "ui-menu.h"
+#include "grafmode.h"
 
 /* Flag value for missing array entry */
 #define MISSING -17