diff --git a/stubs/Collections/Collection.stub b/stubs/Collections/Collection.stub
index 90fb8843..7abdf0da 100644
--- a/stubs/Collections/Collection.stub
+++ b/stubs/Collections/Collection.stub
@@ -7,7 +7,7 @@ use Countable;
 use IteratorAggregate;
 
 /**
- * @template TKey
+ * @template TKey of array-key
  * @template T
  * @extends IteratorAggregate<TKey, T>
  * @extends ArrayAccess<TKey|null, T>