--- a/town.h	Sat Sep 17 13:57:01 2005 +0000
+++ b/town.h	Sun Sep 18 20:56:44 2005 +0000
@@ -138,7 +138,7 @@
 /**
  * Check if a Town really exists.
  */
-static inline bool IsValidTown(Town* town)
+static inline bool IsValidTown(const Town* town)
 {
 	return town->xy != 0; /* XXX: Replace by INVALID_TILE someday */
 }