diff --git a/src/newgrf.h b/src/newgrf.h
--- a/src/newgrf.h
+++ b/src/newgrf.h
@@ -60,6 +60,11 @@ enum GrfSpecFeature {
 	GSF_RAILTYPES,
 	GSF_AIRPORTTILES,
 	GSF_END,
+
+	GSF_FAKE_TOWNS = GSF_END, ///< Fake town GrfSpecFeature for NewGRF debugging (parent scope)
+	GSF_FAKE_END,             ///< End of the fake features
+
+	GSF_INVALID = 0xFF        ///< An invalid spec feature
 };
 
 static const uint32 INVALID_GRFID = 0xFFFFFFFF;