diff --git a/lucene/core/src/java/org/apache/lucene/store/NRTCachingDirectory.java b/lucene/core/src/java/org/apache/lucene/store/NRTCachingDirectory.java
index e0342d54390..8f79fd9e2c4 100644
--- a/lucene/core/src/java/org/apache/lucene/store/NRTCachingDirectory.java
+++ b/lucene/core/src/java/org/apache/lucene/store/NRTCachingDirectory.java
@@ -24,6 +24,7 @@ import java.util.Set;
 
 import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.store.RAMDirectory;      // javadocs
+import org.apache.lucene.util.Accountable;
 import org.apache.lucene.util.IOUtils;
 
 // TODO
@@ -63,7 +64,7 @@ import org.apache.lucene.util.IOUtils;
  * @lucene.experimental
  */
 
-public class NRTCachingDirectory extends FilterDirectory {
+public class NRTCachingDirectory extends FilterDirectory implements Accountable {
 
   private final RAMDirectory cache = new RAMDirectory();
 
@@ -117,12 +118,6 @@ public class NRTCachingDirectory extends FilterDirectory {
     return files.toArray(new String[files.size()]);
   }
 
-  /** Returns how many bytes are being used by the
-   *  RAMDirectory cache */
-  public long cacheRamBytesUsed()  {
-    return cache.ramBytesUsed();
-  }
-
   @Override
   public synchronized void deleteFile(String name) throws IOException {
     if (VERBOSE) {
@@ -261,4 +256,9 @@ public class NRTCachingDirectory extends FilterDirectory {
       }
     }
   }
+
+  @Override
+  public long ramBytesUsed() {
+    return cache.ramBytesUsed();
+  }
 }