diff --git a/src/newgrf_config.h b/src/newgrf_config.h
--- a/src/newgrf_config.h
+++ b/src/newgrf_config.h
@@ -107,7 +107,6 @@ struct GRFError : ZeroedMemoryAllocator 
 	char *data;            ///< Additional data for message and custom_message
 	StringID message;      ///< Default message
 	StringID severity;     ///< Info / Warning / Error / Fatal
-	uint8 num_params;      ///< Number of additinal parameters for message and custom_message (0, 1 or 2)
 	uint32 param_value[2]; ///< Values of GRF parameters to show for message and custom_message
 };