diff --git a/lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java b/lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java
index d28494b5db8..11bde675285 100644
--- a/lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java
+++ b/lucene/src/java/org/apache/lucene/search/cache/ByteValuesCreator.java
@@ -74,7 +74,7 @@ public class ByteValuesCreator extends CachedArrayCreator<ByteValues>
   }
 
   @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) ) {
diff --git a/lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java b/lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java
index a72a322e0dc..13a85585b2e 100644
--- a/lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java
+++ b/lucene/src/java/org/apache/lucene/search/cache/DoubleValuesCreator.java
@@ -74,7 +74,7 @@ public class DoubleValuesCreator extends CachedArrayCreator<DoubleValues>
   }
 
   @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) ) {
diff --git a/lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java b/lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java
index 42191168361..bfd6f070db4 100644
--- a/lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java
+++ b/lucene/src/java/org/apache/lucene/search/cache/FloatValuesCreator.java
@@ -75,7 +75,7 @@ public class FloatValuesCreator extends CachedArrayCreator<FloatValues>
   }
 
   @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) ) {
diff --git a/lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java b/lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java
index 287fcb43113..7c41f4f0cdb 100644
--- a/lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java
+++ b/lucene/src/java/org/apache/lucene/search/cache/IntValuesCreator.java
@@ -75,7 +75,7 @@ public class IntValuesCreator extends CachedArrayCreator<IntValues>
   }
 
   @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) ) {
diff --git a/lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java b/lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java
index f28eee7ce0d..27c1672c9ef 100644
--- a/lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java
+++ b/lucene/src/java/org/apache/lucene/search/cache/LongValuesCreator.java
@@ -75,7 +75,7 @@ public class LongValuesCreator extends CachedArrayCreator<LongValues>
   }
 
   @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) ) {
diff --git a/lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java b/lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java
index 603fcbbb1f8..88c776bf786 100644
--- a/lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java
+++ b/lucene/src/java/org/apache/lucene/search/cache/ShortValuesCreator.java
@@ -75,7 +75,7 @@ public class ShortValuesCreator extends CachedArrayCreator<ShortValues>
   }
 
   @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) ) {