Index: lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java	(revision 1055156)
+++ lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java	(working copy)
@@ -75,7 +75,7 @@
   }
 
   @Override
-  public LongValues validate(LongValues entry, IndexReader reader) throws IOException {
+  public synchronized LongValues validate(LongValues entry, IndexReader reader) throws IOException {
     boolean ok = false;
     
     if( hasOption(OPTION_CACHE_VALUES) ) {
Index: lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java	(revision 1055156)
+++ lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java	(working copy)
@@ -75,7 +75,7 @@
   }
 
   @Override
-  public ShortValues validate(ShortValues entry, IndexReader reader) throws IOException {
+  public synchronized ShortValues validate(ShortValues entry, IndexReader reader) throws IOException {
     boolean ok = false;
     
     if( hasOption(OPTION_CACHE_VALUES) ) {
Index: lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java	(revision 1055156)
+++ lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java	(working copy)
@@ -74,7 +74,7 @@
   }
 
   @Override
-  public ByteValues validate(ByteValues entry, IndexReader reader) throws IOException {
+  public synchronized ByteValues validate(ByteValues entry, IndexReader reader) throws IOException {
     boolean ok = false;
     
     if( hasOption(OPTION_CACHE_VALUES) ) {
Index: lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java	(revision 1055156)
+++ lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java	(working copy)
@@ -75,7 +75,7 @@
   }
 
   @Override
-  public FloatValues validate(FloatValues entry, IndexReader reader) throws IOException {
+  public synchronized FloatValues validate(FloatValues entry, IndexReader reader) throws IOException {
     boolean ok = false;
     
     if( hasOption(OPTION_CACHE_VALUES) ) {
Index: lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java	(revision 1055156)
+++ lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java	(working copy)
@@ -74,7 +74,7 @@
   }
 
   @Override
-  public DoubleValues validate(DoubleValues entry, IndexReader reader) throws IOException {
+  public synchronized DoubleValues validate(DoubleValues entry, IndexReader reader) throws IOException {
     boolean ok = false;
     
     if( hasOption(OPTION_CACHE_VALUES) ) {
Index: lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java	(revision 1055156)
+++ lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java	(working copy)
@@ -75,7 +75,7 @@
   }
 
   @Override
-  public IntValues validate(IntValues entry, IndexReader reader) throws IOException {
+  public synchronized IntValues validate(IntValues entry, IndexReader reader) throws IOException {
     boolean ok = false;
     
     if( hasOption(OPTION_CACHE_VALUES) ) {