diff --git a/src/newgrf.h b/src/newgrf.h
--- a/src/newgrf.h
+++ b/src/newgrf.h
@@ -177,6 +177,8 @@ static inline bool HasGrfMiscBit(GrfMisc
 /* Indicates which are the newgrf features currently loaded ingame */
 extern GRFLoadedFeatures _loaded_newgrf_features;
 
+byte GetGRFContainerVersion();
+
 void LoadNewGRFFile(struct GRFConfig *config, uint file_index, GrfLoadingStage stage, Subdirectory subdir);
 void LoadNewGRF(uint load_index, uint file_index);
 void ReloadNewGRFData(); // in saveload/afterload.cpp