diff --git a/lang/ast/expr/arith.c b/lang/ast/expr/arith.c
index 7657426..fb36d2a 100644
--- a/lang/ast/expr/arith.c
+++ b/lang/ast/expr/arith.c
@@ -598,7 +598,7 @@ struct token_parse_result arith_parse_left_paren(
 		struct ivy_ast_node *msg
 			= b_unbox(struct ivy_ast_node, msg_entry, n_entry);
 
-		if (msg->n_type != IVY_AST_MSG) {
+		if (!msg || msg->n_type != IVY_AST_MSG) {
 			/* this is not a complex message, it's probably a
 			 * call-operator */
 			goto not_complex_msg;