diff --git a/platform/lang-impl/src/com/intellij/ide/projectView/ProjectView.java b/platform/lang-impl/src/com/intellij/ide/projectView/ProjectView.java
index 493c333787a8..fac5b8b2e878 100644
--- a/platform/lang-impl/src/com/intellij/ide/projectView/ProjectView.java
+++ b/platform/lang-impl/src/com/intellij/ide/projectView/ProjectView.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2014 JetBrains s.r.o.
+ * 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.
@@ -39,14 +39,15 @@ public abstract class ProjectView {
   public abstract ActionCallback selectCB(Object element, VirtualFile file, boolean requestFocus);
 
   @NotNull
-  public abstract ActionCallback changeViewCB(@NotNull String viewId, String subId);
+  public abstract ActionCallback changeViewCB(@NotNull String viewId, @Nullable String subId);
 
   @Nullable
   public abstract PsiElement getParentOfCurrentSelection();
 
   // show pane identified by id using default(or currently selected) subId
   public abstract void changeView(@NotNull String viewId);
-  public abstract void changeView(@NotNull String viewId, String subId);
+
+  public abstract void changeView(@NotNull String viewId, @Nullable String subId);
 
   public abstract void changeView();