--- a/src/java.base/share/classes/java/util/stream/DistinctOps.java	Tue Sep 11 13:54:34 2018 -0700
+++ b/src/java.base/share/classes/java/util/stream/DistinctOps.java	Tue Sep 11 14:51:45 2018 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -170,8 +170,7 @@
 
                         @Override
                         public void accept(T t) {
-                            if (!seen.contains(t)) {
-                                seen.add(t);
+                            if (seen.add(t)) {
                                 downstream.accept(t);
                             }
                         }