diff --git a/src/debug.h b/src/debug.h
--- a/src/debug.h
+++ b/src/debug.h
@@ -97,4 +97,7 @@ void CDECL ShowInfoF(const char *str, ..
 
 const char *GetLogPrefix();
 
+/** The real time in the game. */
+extern uint32 _realtime_tick;
+
 #endif /* DEBUG_H */