diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 93a4443f189..cfce0ef8714 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -4385,7 +4385,7 @@ recheck_cast_function_args(List *args, Oid result_type,
 {
 	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
 	int			nargs;
-	Oid			actual_arg_types[FUNC_MAX_ARGS];
+	Oid			actual_arg_types[FUNC_MAX_ARGS] = {0};
 	Oid			declared_arg_types[FUNC_MAX_ARGS];
 	Oid			rettype;
 	ListCell   *lc;