diff --git a/platform/core-api/src/com/intellij/psi/tree/IReparseableElementType.java b/platform/core-api/src/com/intellij/psi/tree/IReparseableElementType.java
index 5a1636d9b4b5..c5772976887c 100644
--- a/platform/core-api/src/com/intellij/psi/tree/IReparseableElementType.java
+++ b/platform/core-api/src/com/intellij/psi/tree/IReparseableElementType.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * Copyright 2000-2013 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.
@@ -19,9 +19,11 @@
  */
 package com.intellij.psi.tree;
 
+import com.intellij.lang.ASTNode;
 import com.intellij.lang.Language;
 import com.intellij.openapi.project.Project;
 import org.jetbrains.annotations.NonNls;
+import org.jetbrains.annotations.Nullable;
 
 public class IReparseableElementType extends ILazyParseableElementType {
   public IReparseableElementType(@NonNls String debugName) {
@@ -43,10 +45,33 @@ public class IReparseableElementType extends ILazyParseableElementType {
    *
    * @param buffer  the content to parse.
    * @param fileLanguage language of the file
-   * @param project the project containing the content.  @return true if the content is valid, false if not
+   * @param project the project containing the content.  
+   * @return true if the content is valid, false if not
    */
 
   public boolean isParsable(CharSequence buffer, Language fileLanguage, final Project project) {
     return false;
   }
+
+  /**
+   * The same as {@link this#isParsable(CharSequence, com.intellij.lang.Language, com.intellij.openapi.project.Project)} 
+   * but with parent ASTNode of the old node.
+   * 
+   * Override this method only if you really understand what are doing.
+   * In other cases override {@link this#isParsable(CharSequence, com.intellij.lang.Language, com.intellij.openapi.project.Project)}
+   * 
+   * Known valid use-case:
+   *  Indent-based languages. You should know about parent indent in order to decide if block is reparsable with given text.
+   *  Because if indent of some line became equals to parent indent then the block should have another parent or block is not block anymore.
+   *  So it cannot be reparsed and whole file or parent block should be reparsed.
+   * 
+   * @param parent parent node of old (or collapsed) reparsable node.
+   * @param buffer the content to parse.
+   * @param fileLanguage language of the file
+   * @param project the project containing the content.  
+   * @return true if the content is valid, false if not
+   */
+  public boolean isParsable(@Nullable ASTNode parent, CharSequence buffer, Language fileLanguage, final Project project) {
+    return isParsable(buffer, fileLanguage, project);
+  }
 }
diff --git a/platform/core-impl/src/com/intellij/psi/impl/source/text/BlockSupportImpl.java b/platform/core-impl/src/com/intellij/psi/impl/source/text/BlockSupportImpl.java
index 695e948cce32..b5070410025f 100644
--- a/platform/core-impl/src/com/intellij/psi/impl/source/text/BlockSupportImpl.java
+++ b/platform/core-impl/src/com/intellij/psi/impl/source/text/BlockSupportImpl.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2009 JetBrains s.r.o.
+ * Copyright 2000-2013 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.
@@ -112,7 +112,7 @@ public class BlockSupportImpl extends BlockSupport {
 
           CharSequence newTextStr = newFileText.subSequence(start, end);
 
-          if (reparseable.isParsable(newTextStr, baseLanguage, project)) {
+          if (reparseable.isParsable(node.getTreeParent(), newTextStr, baseLanguage, project)) {
             ASTNode chameleon = reparseable.createNode(newTextStr);
             if (chameleon != null) {
               DummyHolder holder = DummyHolderFactory.createHolder(fileImpl.getManager(), null, node.getPsi(), charTable);