diff --git a/java/openapi/src/com/intellij/openapi/roots/libraries/JarVersionDetectionUtil.java b/java/openapi/src/com/intellij/openapi/roots/libraries/JarVersionDetectionUtil.java
index 245ca3a459d5..8791a54357a8 100644
--- a/java/openapi/src/com/intellij/openapi/roots/libraries/JarVersionDetectionUtil.java
+++ b/java/openapi/src/com/intellij/openapi/roots/libraries/JarVersionDetectionUtil.java
@@ -1,18 +1,4 @@
-/*
- * Copyright 2000-2016 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 2000-2019 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.libraries;
 
 import com.intellij.openapi.diagnostic.Logger;
@@ -58,7 +44,8 @@ public class JarVersionDetectionUtil {
            getMainAttribute(jarRoot, Attributes.Name.IMPLEMENTATION_VERSION) : null;
   }
 
-  private static String getMainAttribute(VirtualFile jarRoot, Attributes.Name attribute) {
+  @Nullable
+  public static String getMainAttribute(@NotNull VirtualFile jarRoot, @NotNull Attributes.Name attribute) {
     VirtualFile manifestFile = jarRoot.findFileByRelativePath(JarFile.MANIFEST_NAME);
     if (manifestFile != null) {
       try (InputStream stream = manifestFile.getInputStream()) {