diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 8fe4219a12d..7736c778374 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -57,6 +57,11 @@ New features
 * LUCENE-5098: New broadword utility methods in oal.util.BroadWord.
   (Paul Elschot via Adrien Grand, Dawid Weiss)
 
+API Changes
+
+* LUCENE-5094: Add ramBytesUsed() to MultiDocValues.OrdinalMap.
+  (Robert Muir)
+
 ======================= Lucene 4.4.0 =======================
 
 Changes in backwards compatibility policy
diff --git a/lucene/core/src/java/org/apache/lucene/index/MultiDocValues.java b/lucene/core/src/java/org/apache/lucene/index/MultiDocValues.java
index adc749ab6bb..c793516c802 100644
--- a/lucene/core/src/java/org/apache/lucene/index/MultiDocValues.java
+++ b/lucene/core/src/java/org/apache/lucene/index/MultiDocValues.java
@@ -360,6 +360,17 @@ public class MultiDocValues {
     public long getValueCount() {
       return globalOrdDeltas.size();
     }
+    
+    /** 
+     * Returns total byte size used by this ordinal map. 
+     */
+    public long ramBytesUsed() {
+      long size = globalOrdDeltas.ramBytesUsed() + subIndexes.ramBytesUsed();
+      for (int i = 0; i < ordDeltas.length; i++) {
+        size += ordDeltas[i].ramBytesUsed();
+      }
+      return size;
+    }
   }
   
   /**