diff --git a/src/rev.h b/src/rev.h
--- a/src/rev.h
+++ b/src/rev.h
@@ -6,6 +6,7 @@
 #define REV_H
 
 extern const char _openttd_revision[];
+extern const byte _openttd_revision_modified;
 extern const uint32 _openttd_newgrf_version;
 
 #endif /* REV_H */