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 0d6f75a35ddf..589fdea58b3e 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
@@ -12,6 +12,8 @@ import com.intellij.util.indexing.IndexExtension;
 import com.intellij.util.indexing.IndexId;
 import com.intellij.util.indexing.InvertedIndex;
 import com.intellij.util.indexing.impl.*;
+import com.intellij.util.indexing.impl.forward.KeyCollectionForwardIndexAccessor;
+import com.intellij.util.indexing.impl.forward.PersistentMapBasedForwardIndex;
 import com.intellij.util.io.*;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jps.backwardRefs.NameEnumerator;
@@ -198,6 +200,7 @@ public class CompilerReferenceIndex<Input> {
   
   public void setRebuildRequestCause(Throwable e) {
     myRebuildRequestCause = e;
+    LOG.error(e);
   }
 
   private static void close(InvertedIndex<?, ?, ?> index, CommonProcessors.FindFirstProcessor<Exception> exceptionProcessor) {
@@ -231,17 +234,8 @@ public class CompilerReferenceIndex<Input> {
       throws IOException {
       super(extension,
             createIndexStorage(extension.getKeyDescriptor(), extension.getValueExternalizer(), extension.getName(), indexDir, readOnly),
-            readOnly ? null : new KeyCollectionBasedForwardIndex<Key, Value>(extension) {
-              @NotNull
-              @Override
-              public PersistentHashMap<Integer, Collection<Key>> createMap() throws IOException {
-                IndexId<Key, Value> id = getIndexExtension().getName();
-                return new PersistentHashMap<>(new File(indexDir, id.getName() + ".inputs"),
-                                               EnumeratorIntegerDescriptor.INSTANCE,
-                                               new InputIndexDataExternalizer<>(extension.getKeyDescriptor(),
-                                                                                id));
-              }
-            });
+            readOnly ? null : new PersistentMapBasedForwardIndex(new File(indexDir, extension.getName().getName() + ".inputs")),
+            readOnly ? null : new KeyCollectionForwardIndexAccessor<>(extension));
     }
 
     @Override
diff --git a/platform/util/src/com/intellij/util/indexing/impl/forward/AbstractForwardIndexAccessor.java b/platform/util/src/com/intellij/util/indexing/impl/forward/AbstractForwardIndexAccessor.java
index b362e630beb2..9a59d1b8224a 100644
--- a/platform/util/src/com/intellij/util/indexing/impl/forward/AbstractForwardIndexAccessor.java
+++ b/platform/util/src/com/intellij/util/indexing/impl/forward/AbstractForwardIndexAccessor.java
@@ -4,6 +4,7 @@ package com.intellij.util.indexing.impl.forward;
 import com.intellij.openapi.util.ThreadLocalCachedByteArray;
 import com.intellij.openapi.util.io.BufferExposingByteArrayOutputStream;
 import com.intellij.openapi.util.io.ByteArraySequence;
+import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.indexing.impl.InputDataDiffBuilder;
 import com.intellij.util.io.DataExternalizer;
 import com.intellij.util.io.DataOutputStream;
@@ -38,7 +39,7 @@ public abstract class AbstractForwardIndexAccessor<Key, Value, DataType, Input>
   @Nullable
   @Override
   public ByteArraySequence serializeIndexedData(@Nullable Map<Key, Value> map, @Nullable Input content) throws IOException {
-    if (map == null) return null;
+    if (ContainerUtil.isEmpty(map)) return null;
     return serializeToByteSeq(convertToDataType(map, content), myDataTypeExternalizer, map.size());
   }
 
diff --git a/platform/util/src/com/intellij/util/indexing/impl/forward/KeyCollectionForwardIndexAccessor.java b/platform/util/src/com/intellij/util/indexing/impl/forward/KeyCollectionForwardIndexAccessor.java
index b6623bcd05e1..4b29f8544a62 100644
--- a/platform/util/src/com/intellij/util/indexing/impl/forward/KeyCollectionForwardIndexAccessor.java
+++ b/platform/util/src/com/intellij/util/indexing/impl/forward/KeyCollectionForwardIndexAccessor.java
@@ -2,6 +2,7 @@
 package com.intellij.util.indexing.impl.forward;
 
 import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.indexing.IndexExtension;
 import com.intellij.util.indexing.IndexId;
 import com.intellij.util.indexing.impl.CollectionInputDataDiffBuilder;
 import com.intellij.util.indexing.impl.InputDataDiffBuilder;
@@ -21,6 +22,10 @@ public class KeyCollectionForwardIndexAccessor<Key, Value, Input> extends Abstra
     super(externalizer);
   }
 
+  public KeyCollectionForwardIndexAccessor(@NotNull IndexExtension<Key, Value, Input> extension) {
+    this(extension.getKeyDescriptor(), extension.getName());
+  }
+
   public KeyCollectionForwardIndexAccessor(@NotNull KeyDescriptor<Key> externalizer, @NotNull IndexId<Key, Value> indexId) {
     super(new InputIndexDataExternalizer<>(externalizer, indexId));
   }