Project SDK is not saved on change

platform/projectModel-impl/src/com/intellij/openapi/roots/impl/ProjectRootManagerImpl.java

@@ -1,18 +1,4 @@
-/*
- * Copyright 2000-2017 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 
 package com.intellij.openapi.roots.impl;
 
@@ -236,6 +222,7 @@ public class ProjectRootManagerImpl extends ProjectRootManagerEx implements Pers
   }
 
   private void projectJdkChanged() {
+    incModificationCount();
     mergeRootsChangesDuring(() -> myProjectJdkEventDispatcher.getMulticaster().projectJdkChanged());
     Sdk sdk = getProjectSdk();
     for (ProjectExtension extension : Extensions.getExtensions(ProjectExtension.EP_NAME, myProject)) {