Track arg_type_info ownership properly
diff --git a/common.h b/common.h
index 9f0e8e0..2741662 100644
--- a/common.h
+++ b/common.h
@@ -55,6 +55,7 @@
 	const char * name;
 	struct param *params;
 	struct arg_type_info *return_info;
+	int own_return_info;
 	size_t num_params;
 	Function * next;
 };