diff --git a/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/DiscoveredTestsIndex.java b/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/DiscoveredTestsIndex.java
index 3b4574c59898..e1849714bbd2 100644
--- a/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/DiscoveredTestsIndex.java
+++ b/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/DiscoveredTestsIndex.java
@@ -20,7 +20,7 @@ public class DiscoveredTestsIndex extends MapReduceIndex<Integer, TIntArrayList,
   protected DiscoveredTestsIndex(@NotNull File file) throws IOException {
     super(INDEX_EXTENSION,
           new MyIndexStorage(file),
-          new PersistentMapBasedForwardIndex(new File(file, "forward.idx")),
+          new PersistentMapBasedForwardIndex(new File(file, "forward.idx"), false),
           new KeyCollectionForwardIndexAccessor<>(new IntCollectionDataExternalizer()));
   }
 
diff --git a/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/TestFilesIndex.java b/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/TestFilesIndex.java
index f4c9da8d4a8c..e3ae818a8a79 100644
--- a/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/TestFilesIndex.java
+++ b/java/execution/impl/src/com/intellij/execution/testDiscovery/indices/TestFilesIndex.java
@@ -21,7 +21,7 @@ public class TestFilesIndex extends MapReduceIndex<Integer, Void, UsedSources> {
   protected TestFilesIndex(@NotNull File file) throws IOException {
     super(INDEX_EXTENSION,
           new MyIndexStorage(file),
-          new PersistentMapBasedForwardIndex(new File(file, "forward.idx")),
+          new PersistentMapBasedForwardIndex(new File(file, "forward.idx"), false),
           new KeyCollectionForwardIndexAccessor<>(new IntCollectionDataExternalizer()));
   }
 
diff --git a/java/java-tests/testSrc/com/intellij/java/index/StringIndex.java b/java/java-tests/testSrc/com/intellij/java/index/StringIndex.java
index d0e01aa2ac70..cbc6e759c7c3 100644
--- a/java/java-tests/testSrc/com/intellij/java/index/StringIndex.java
+++ b/java/java-tests/testSrc/com/intellij/java/index/StringIndex.java
@@ -103,7 +103,7 @@ public class StringIndex {
     };
     myIndex = new MapReduceIndex<String, String, PathContentPair>(extension,
                                                                   storage,
-                                                                  new PersistentMapBasedForwardIndex(forwardIndexFile),
+                                                                  new PersistentMapBasedForwardIndex(forwardIndexFile, false),
                                                                   new KeyCollectionForwardIndexAccessor<>(anotherStringExternalizer)) {
       @Override
       public void checkCanceled() {
diff --git a/jps/jps-builders/src/org/jetbrains/jps/backwardRefs/index/CompilerReferenceIndex.java b/jps/jps-builders/src/org/jetbrains/jps/backwardRefs/index/CompilerReferenceIndex.java
index 1718a31be0c3..0baed9958e3e 100644
--- a/jps/jps-builders/src/org/jetbrains/jps/backwardRefs/index/CompilerReferenceIndex.java
+++ b/jps/jps-builders/src/org/jetbrains/jps/backwardRefs/index/CompilerReferenceIndex.java
@@ -273,7 +273,7 @@ public class CompilerReferenceIndex<Input> {
       throws IOException {
       super(extension,
             createIndexStorage(extension.getKeyDescriptor(), extension.getValueExternalizer(), extension.getName(), indexDir, readOnly),
-            readOnly ? null : new PersistentMapBasedForwardIndex(new File(indexDir, extension.getName().getName() + ".inputs")),
+            readOnly ? null : new PersistentMapBasedForwardIndex(new File(indexDir, extension.getName().getName() + ".inputs"), false),
             readOnly ? null : new KeyCollectionForwardIndexAccessor<>(extension));
     }
 
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/VfsAwareMapReduceIndex.java b/platform/lang-impl/src/com/intellij/util/indexing/VfsAwareMapReduceIndex.java
index e4b7a551e699..548780555bbd 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/VfsAwareMapReduceIndex.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/VfsAwareMapReduceIndex.java
@@ -437,7 +437,7 @@ public class VfsAwareMapReduceIndex<Key, Value, Input> extends MapReduceIndex<Ke
     if (!shouldCreateForwardIndex(indexExtension)) return null;
     if (indexExtension instanceof SingleEntryFileBasedIndexExtension<?>) return new EmptyForwardIndex(); // indexStorage and forwardIndex are same here
     File indexStorageFile = IndexInfrastructure.getInputIndexStorageFile((ID<?, ?>)indexExtension.getName());
-    return new PersistentMapBasedForwardIndex(indexStorageFile, false);
+    return new PersistentMapBasedForwardIndex(indexStorageFile, false, false);
   }
 
   private static boolean shouldCreateForwardIndex(@NotNull IndexExtension<?, ?, ?> indexExtension) {
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/hash/FileContentHashIndex.java b/platform/lang-impl/src/com/intellij/util/indexing/hash/FileContentHashIndex.java
index ad65ba28491e..e66f22cb589d 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/hash/FileContentHashIndex.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/hash/FileContentHashIndex.java
@@ -17,7 +17,7 @@ public class FileContentHashIndex extends VfsAwareMapReduceIndex<Integer, Void,
   FileContentHashIndex(@NotNull FileContentHashIndexExtension extension, IndexStorage<Integer, Void> storage) throws IOException {
     super(extension,
           storage,
-          new PersistentMapBasedForwardIndex(IndexInfrastructure.getInputIndexStorageFile(extension.getName())),
+          new PersistentMapBasedForwardIndex(IndexInfrastructure.getInputIndexStorageFile(extension.getName()), false),
           new MapForwardIndexAccessor<>(new InputMapExternalizer<>(extension)), null, null);
   }
 
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/snapshot/SnapshotInputMappings.java b/platform/lang-impl/src/com/intellij/util/indexing/snapshot/SnapshotInputMappings.java
index 7d1f6f33de10..d5d1c07795e8 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/snapshot/SnapshotInputMappings.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/snapshot/SnapshotInputMappings.java
@@ -208,7 +208,7 @@ public class SnapshotInputMappings<Key, Value, Input> implements UpdatableSnapsh
     if (SharedIndicesData.ourFileSharedIndicesEnabled && !SharedIndicesData.DO_CHECKS) return null;
     final File saved = new File(IndexInfrastructure.getPersistentIndexRootDir(myIndexId), "values");
     try {
-      return new PersistentMapBasedForwardIndex(saved);
+      return new PersistentMapBasedForwardIndex(saved, false);
     }
     catch (IOException ex) {
       IOUtil.deleteAllFilesStartingWith(saved);
diff --git a/platform/util/src/com/intellij/util/indexing/impl/forward/PersistentMapBasedForwardIndex.java b/platform/util/src/com/intellij/util/indexing/impl/forward/PersistentMapBasedForwardIndex.java
index 76d2ea5e0654..d60515485170 100644
--- a/platform/util/src/com/intellij/util/indexing/impl/forward/PersistentMapBasedForwardIndex.java
+++ b/platform/util/src/com/intellij/util/indexing/impl/forward/PersistentMapBasedForwardIndex.java
@@ -20,26 +20,31 @@ public class PersistentMapBasedForwardIndex implements ForwardIndex {
   @NotNull
   private final File myMapFile;
   private final boolean myUseChunks;
+  private final boolean myReadOnly;
 
-  public PersistentMapBasedForwardIndex(@NotNull File mapFile) throws IOException {
-    this(mapFile, true);
+  public PersistentMapBasedForwardIndex(@NotNull File mapFile, boolean isReadOnly) throws IOException {
+    this(mapFile, true, isReadOnly);
   }
 
-  public PersistentMapBasedForwardIndex(@NotNull File mapFile, boolean useChunks) throws IOException {
+  public PersistentMapBasedForwardIndex(@NotNull File mapFile, boolean useChunks, boolean isReadOnly) throws IOException {
     myPersistentMap = createMap(mapFile);
     myMapFile = mapFile;
     myUseChunks = useChunks;
+    myReadOnly = isReadOnly;
   }
 
   @NotNull
   protected PersistentHashMap<Integer, ByteArraySequence> createMap(File file) throws IOException {
     Boolean oldHasNoChunksValue = PersistentHashMapValueStorage.CreationTimeOptions.HAS_NO_CHUNKS.get();
     PersistentHashMapValueStorage.CreationTimeOptions.HAS_NO_CHUNKS.set(!myUseChunks);
+    Boolean previousReadOnly = PersistentHashMapValueStorage.CreationTimeOptions.READONLY.get();
+    PersistentHashMapValueStorage.CreationTimeOptions.READONLY.set(myReadOnly);
     try {
       return new PersistentHashMap<>(file, EnumeratorIntegerDescriptor.INSTANCE, ByteSequenceDataExternalizer.INSTANCE);
     }
     finally {
       PersistentHashMapValueStorage.CreationTimeOptions.HAS_NO_CHUNKS.set(oldHasNoChunksValue);
+      PersistentHashMapValueStorage.CreationTimeOptions.READONLY.set(previousReadOnly);
     }
   }
 
diff --git a/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogPathsIndex.java b/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogPathsIndex.java
index 190ea7c6f726..e1cdfdee9c1c 100644
--- a/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogPathsIndex.java
+++ b/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogPathsIndex.java
@@ -59,7 +59,7 @@ public class VcsLogPathsIndex extends VcsLogFullDetailsIndex<List<VcsLogPathsInd
   @Override
   protected Pair<ForwardIndex, ForwardIndexAccessor<Integer, List<ChangeKind>>> createdForwardIndex() throws IOException {
     if (!isPathsForwardIndexRequired()) return null;
-    return Pair.create(new PersistentMapBasedForwardIndex(myStorageId.getStorageFile(myName + ".idx")),
+    return Pair.create(new PersistentMapBasedForwardIndex(myStorageId.getStorageFile(myName + ".idx"), false),
                        new KeyCollectionForwardIndexAccessor<Integer, List<ChangeKind>>(new IntCollectionDataExternalizer()) {
                          @Nullable
                          @Override
diff --git a/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogUserIndex.java b/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogUserIndex.java
index 9df80592203f..5d553d13d6a5 100644
--- a/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogUserIndex.java
+++ b/platform/vcs-log/impl/src/com/intellij/vcs/log/data/index/VcsLogUserIndex.java
@@ -52,7 +52,7 @@ public class VcsLogUserIndex extends VcsLogFullDetailsIndex<Void, VcsShortCommit
   @Nullable
   @Override
   protected Pair<ForwardIndex, ForwardIndexAccessor<Integer, Void>> createdForwardIndex() throws IOException {
-    return Pair.create(new PersistentMapBasedForwardIndex(myStorageId.getStorageFile(myName + ".idx")),
+    return Pair.create(new PersistentMapBasedForwardIndex(myStorageId.getStorageFile(myName + ".idx"), false ),
                        new KeyCollectionForwardIndexAccessor<>(new IntCollectionDataExternalizer()));
   }