diff --git a/quickjs.c b/quickjs.c
index 3696011..d662eb3 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -15005,6 +15005,8 @@ static JSValue js_build_mapped_arguments(JSContext *ctx, int argc,
     if (JS_IsException(val))
         return val;
     p = JS_VALUE_GET_OBJ(val);
+    p->u.array.u.values = NULL;
+    p->u.array.count = 0;
 
     /* add the length field (cannot fail) */
     pr = add_property(ctx, p, JS_ATOM_length,