diff --git a/platform/diff-impl/src/com/intellij/diff/merge/TextMergeTool.java b/platform/diff-impl/src/com/intellij/diff/merge/TextMergeTool.java
index a0c1ca24d1b3..26e58ddabf0e 100644
--- a/platform/diff-impl/src/com/intellij/diff/merge/TextMergeTool.java
+++ b/platform/diff-impl/src/com/intellij/diff/merge/TextMergeTool.java
@@ -701,13 +701,18 @@ public class TextMergeTool implements MergeTool {
         }
 
         private void registerUndoRedo(final boolean undo) {
+          Project project = getProject();
+          if (project == null) {
+            return;
+          }
+
           List<TextMergeChange> affectedChanges = getAffectedChanges();
           final List<TextMergeChange.State> states = new ArrayList<TextMergeChange.State>(affectedChanges.size());
           for (TextMergeChange change : affectedChanges) {
             states.add(change.storeState());
           }
 
-          UndoManager.getInstance(getProject()).undoableActionPerformed(new BasicUndoableAction(myDocument) {
+          UndoManager.getInstance(project).undoableActionPerformed(new BasicUndoableAction(myDocument) {
             @Override
             public void undo() throws UnexpectedUndoException {
               if (undo) restoreStates(states);
diff --git a/platform/platform-api/src/com/intellij/openapi/command/undo/UndoManager.java b/platform/platform-api/src/com/intellij/openapi/command/undo/UndoManager.java
index bcbe7afb9d6e..b6f60a55f968 100644
--- a/platform/platform-api/src/com/intellij/openapi/command/undo/UndoManager.java
+++ b/platform/platform-api/src/com/intellij/openapi/command/undo/UndoManager.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * Copyright 2000-2015 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.
@@ -21,12 +21,13 @@ import com.intellij.openapi.fileEditor.FileEditor;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Key;
 import com.intellij.openapi.util.Pair;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public abstract class UndoManager {
   public static final Key<Document> ORIGINAL_DOCUMENT = new Key<Document>("ORIGINAL_DOCUMENT");
 
-  public static UndoManager getInstance(Project project) {
+  public static UndoManager getInstance(@NotNull Project project) {
     return project.getComponent(UndoManager.class);
   }