diff --git a/aio/content/tutorial/toh-pt4.md b/aio/content/tutorial/toh-pt4.md
index 4d9f2ecb1a..6223933b46 100644
--- a/aio/content/tutorial/toh-pt4.md
+++ b/aio/content/tutorial/toh-pt4.md
@@ -3,7 +3,7 @@
 The Tour of Heroes `HeroesComponent` is currently getting and displaying fake data.
 
 After the refactoring in this tutorial, `HeroesComponent` will be lean and focused on supporting the view.
-It will also be easier to unit-test with a mock services.
+It will also be easier to unit-test with a mock service.
 
 ## Why services