diff --git a/sc/sc0101.cpp b/sc/sc0101.cpp
index 8ec1ce037..7c2674f39 100755
--- a/sc/sc0101.cpp
+++ b/sc/sc0101.cpp
@@ -1,6 +1,7 @@
 #include <execp.h>
 #include <mailbox.h>
 #include <real.h>
+#include <relation.h>
 
 #include "../cg/cglib01.h"
 #include "../cg/cgpagame.h"