diff --git a/packages/dcons/src/dcons.ts b/packages/dcons/src/dcons.ts
index 5da844386d..4fbb504f26 100644
--- a/packages/dcons/src/dcons.ts
+++ b/packages/dcons/src/dcons.ts
@@ -510,7 +510,10 @@ export class DCons<T>
     shuffle(iter?: number, rnd: IRandom = SYSTEM) {
         if (this._length < 2) return this;
         for (
-            iter = iter ?? Math.ceil(1.5 * Math.log2(this._length));
+            iter =
+                iter !== undefined
+                    ? iter
+                    : Math.ceil(1.5 * Math.log2(this._length));
             iter > 0;
             iter--
         ) {