diff --git a/src/openttd.h b/src/openttd.h
--- a/src/openttd.h
+++ b/src/openttd.h
@@ -81,6 +81,6 @@ void HandleExitGameRequest();
 
 void SwitchToMode(SwitchMode new_mode);
 
-void RequestNewGRFScan(struct NewGRFScanCallback *callback = nullptr);
+bool RequestNewGRFScan(struct NewGRFScanCallback *callback = nullptr);
 
 #endif /* OPENTTD_H */