diff --git a/lucene/core/src/java/org/apache/lucene/codecs/lucene3x/Lucene3xCodec.java b/lucene/core/src/java/org/apache/lucene/codecs/lucene3x/Lucene3xCodec.java
index 888c1b8..de98a51 100644
--- a/lucene/core/src/java/org/apache/lucene/codecs/lucene3x/Lucene3xCodec.java
+++ b/lucene/core/src/java/org/apache/lucene/codecs/lucene3x/Lucene3xCodec.java
@@ -76,12 +76,12 @@ public class Lucene3xCodec extends Codec {
   private final DocValuesFormat docValuesFormat = new DocValuesFormat() {
     @Override
     public PerDocConsumer docsConsumer(PerDocWriteState state) throws IOException {
-      return null;
+      throw new UnsupportedOperationException("this codec doesn't support DocValues");
     }
 
     @Override
     public PerDocProducer docsProducer(SegmentReadState state) throws IOException {
-      return null;
+      return null; // that if fine since null means simply no DocValues available
     }
 
     @Override
diff --git a/lucene/core/src/java/org/apache/lucene/index/SegmentMerger.java b/lucene/core/src/java/org/apache/lucene/index/SegmentMerger.java
index da7db93..a0bca20 100644
--- a/lucene/core/src/java/org/apache/lucene/index/SegmentMerger.java
+++ b/lucene/core/src/java/org/apache/lucene/index/SegmentMerger.java
@@ -367,24 +367,26 @@ final class SegmentMerger {
   }
 
   private void mergePerDoc(SegmentWriteState segmentWriteState) throws IOException {
-      final PerDocConsumer docsConsumer = codec.docValuesFormat()
+    final PerDocConsumer docsConsumer;
+    try {  
+      docsConsumer = codec.docValuesFormat()
           .docsConsumer(new PerDocWriteState(segmentWriteState));
+    } catch (UnsupportedOperationException ex) {
       // TODO: remove this check when 3.x indexes are no longer supported
       // (3.x indexes don't have docvalues)
-      if (docsConsumer == null) {
-        return;
-      }
-      boolean success = false;
-      try {
-        docsConsumer.merge(mergeState);
-        success = true;
-      } finally {
-        if (success) {
-          IOUtils.close(docsConsumer);
-        } else {
-          IOUtils.closeWhileHandlingException(docsConsumer);
-        }
+      return;
+    }
+    boolean success = false;
+    try {
+      docsConsumer.merge(mergeState);
+      success = true;
+    } finally {
+      if (success) {
+        IOUtils.close(docsConsumer);
+      } else {
+        IOUtils.closeWhileHandlingException(docsConsumer);
       }
+    }
   }
   
   private void mergeNorms(SegmentWriteState segmentWriteState) throws IOException {