diff --git a/Python/ast.c b/Python/ast.c
index 4fa98b1..76588c3 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -1366,7 +1366,7 @@
     PyObject *argname;
     node *ch;
     expr_ty expression, annotation;
-    arg_ty arg;
+    arg_ty arg = NULL;
     int i = start;
     int j = 0; /* index for kwdefaults and kwonlyargs */
 
@@ -1462,7 +1462,7 @@
     int nposdefaults = 0, found_default = 0;
     asdl_seq *posargs, *posdefaults, *kwonlyargs, *kwdefaults;
     arg_ty vararg = NULL, kwarg = NULL;
-    arg_ty arg;
+    arg_ty arg = NULL;
     node *ch;
 
     if (TYPE(n) == parameters) {