diff --git a/js/src/builtin/Array.cpp b/js/src/builtin/Array.cpp
index 46068590c8dc..9034aa72fe1c 100644
--- a/js/src/builtin/Array.cpp
+++ b/js/src/builtin/Array.cpp
@@ -4128,6 +4128,15 @@ static bool array_proto_finish(JSContext* cx, JS::HandleObject ctor,
     return false;
   }
 
+#ifdef NIGHTLY_BUILD
+  if (cx->realm()->creationOptions().getArrayGroupingEnabled()) {
+    if (!DefineDataProperty(cx, unscopables, cx->names().groupBy, value) ||
+        !DefineDataProperty(cx, unscopables, cx->names().groupByToMap, value)) {
+      return false;
+    }
+  }
+#endif
+
 #ifdef ENABLE_CHANGE_ARRAY_BY_COPY
   if (cx->options().changeArrayByCopy()) {
     if (!DefineDataProperty(cx, unscopables, cx->names().withAt, value) ||
diff --git a/js/src/tests/non262/Array/unscopables.js b/js/src/tests/non262/Array/unscopables.js
index 7f17a4b37a09..226b7314dab1 100644
--- a/js/src/tests/non262/Array/unscopables.js
+++ b/js/src/tests/non262/Array/unscopables.js
@@ -44,6 +44,11 @@ if (getBuildConfiguration()['change-array-by-copy'] && getRealmConfiguration().e
     expectedKeys.push("withAt", "withReversed", "withSorted", "withSpliced");
 }
 
+if (!getBuildConfiguration().release_or_beta && getRealmConfiguration().enableArrayGrouping) {
+    expectedKeys.push("groupBy", "groupByToMap");
+    expectedKeys.sort();
+}
+
 assertDeepEq(keys, expectedKeys);
 
 for (let key of keys)