diff --git a/src/openttd.h b/src/openttd.h
--- a/src/openttd.h
+++ b/src/openttd.h
@@ -20,7 +20,6 @@ typedef EngineID *EngineList; ///< engin
 
 /* IDs used in Pools */
 typedef uint16 WaypointID;
-typedef uint16 SignID;
 typedef uint16 EngineRenewID;
 
 enum GameModes {
diff --git a/src/signs.h b/src/signs.h
--- a/src/signs.h
+++ b/src/signs.h
@@ -7,6 +7,7 @@
 
 #include "oldpool.h"
 
+typedef uint16 SignID;
 struct Sign;
 DECLARE_OLD_POOL(Sign, Sign, 2, 16000)