diff --git a/src/signs.cpp b/src/signs.cpp
--- a/src/signs.cpp
+++ b/src/signs.cpp
@@ -6,7 +6,8 @@
 #include "openttd.h"
 #include "landscape.h"
 #include "player_func.h"
-#include "signs.h"
+#include "signs_base.h"
+#include "signs_func.h"
 #include "saveload.h"
 #include "command_func.h"
 #include "variables.h"