diff --git a/src/content/graphql-js/APIReference-TypeSystem.md b/src/content/graphql-js/APIReference-TypeSystem.md
index 4191d1130a..dad34ccd45 100644
--- a/src/content/graphql-js/APIReference-TypeSystem.md
+++ b/src/content/graphql-js/APIReference-TypeSystem.md
@@ -189,7 +189,7 @@ validator and executor.
 
 ```js
 var MyAppSchema = new GraphQLSchema({
-  query: MyAppQueryRootType
+  query: MyAppQueryRootType,
   mutation: MyAppMutationRootType
 });
 ```