Fix a typo
diff --git a/NULL_SAFETY_README.md b/NULL_SAFETY_README.md
index e427a70..77963a0 100644
--- a/NULL_SAFETY_README.md
+++ b/NULL_SAFETY_README.md
@@ -19,7 +19,7 @@
 
 <!-- TODO(srawlins): point to details somewhere. -->
 
-Here is the standard way of defining a mock for the Foo class:
+Here is the standard way of defining a mock for the HttpServer class:
 
 ```dart
 class MockHttpServer extends Mock implements HttpServer {}