diff --git a/Sources/Apollo/Collections.swift b/Sources/Apollo/Collections.swift
index 0020d9e7fe..f9282fba75 100644
--- a/Sources/Apollo/Collections.swift
+++ b/Sources/Apollo/Collections.swift
@@ -44,7 +44,7 @@ extension GroupedSequence: Sequence {
 struct GroupedSequenceIterator<Key: Equatable, Value>: IteratorProtocol {
   private var base: GroupedSequence<Key, Value>
   
-  private var keyIterator: EnumeratedIterator<IndexingIterator<Array<Key>>>
+  private var keyIterator: EnumeratedSequence<Array<Key>>.Iterator
   
   init(base: GroupedSequence<Key, Value>) {
     self.base = base