diff --git a/Python/ast.c b/Python/ast.c
index 7a1b5bc..e14ff3a 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -1934,10 +1934,14 @@
         }
         else if (TYPE(ch) == STAR) {
             vararg = ast_for_expr(c, CHILD(n, i+1));
+            if (!vararg)
+                return NULL;
             i++;
         }
         else if (TYPE(ch) == DOUBLESTAR) {
             kwarg = ast_for_expr(c, CHILD(n, i+1));
+            if (!kwarg)
+                return NULL;
             i++;
         }
     }