diff --git a/src/main/java/org/elasticsearch/action/admin/indices/stats/CommonStatsFlags.java b/src/main/java/org/elasticsearch/action/admin/indices/stats/CommonStatsFlags.java
index 10defa43c57..8aadd618fe0 100644
--- a/src/main/java/org/elasticsearch/action/admin/indices/stats/CommonStatsFlags.java
+++ b/src/main/java/org/elasticsearch/action/admin/indices/stats/CommonStatsFlags.java
@@ -169,6 +169,8 @@ public class CommonStatsFlags implements Streamable {
     }
     
     public static enum Flag {
+        // Do not change the order of these flags we use
+        // the ordinal for encoding! Only append to the end!
         Store("store"),
         Indexing("indexing"),
         Get("get"),
diff --git a/src/test/java/org/elasticsearch/test/integration/indices/stats/SimpleIndexStatsTests.java b/src/test/java/org/elasticsearch/test/integration/indices/stats/SimpleIndexStatsTests.java
index e68e2972b89..3927b5c7867 100644
--- a/src/test/java/org/elasticsearch/test/integration/indices/stats/SimpleIndexStatsTests.java
+++ b/src/test/java/org/elasticsearch/test/integration/indices/stats/SimpleIndexStatsTests.java
@@ -20,6 +20,7 @@
 package org.elasticsearch.test.integration.indices.stats;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.EnumSet;
 import java.util.Random;
 
@@ -285,6 +286,17 @@ public class SimpleIndexStatsTests extends AbstractNodesTests {
         }
     }
     
+    @Test
+    public void testFlagOrdinalOrder() {
+        Flag[] flags = new Flag[] { Flag.Store, Flag.Indexing, Flag.Get, Flag.Search, Flag.Merge, Flag.Flush, Flag.Refresh,
+                Flag.FilterCache, Flag.IdCache, Flag.FieldData, Flag.Docs, Flag.Warmer };
+        
+        assertThat(flags.length, equalTo(Flag.values().length));
+        for (int i = 0; i < flags.length; i++) {
+            assertThat("ordinal has changed - this breaks the wire protocol. Only append to new values", i, equalTo(flags[i].ordinal()));
+        }
+    }
+    
     private static void set(Flag flag, IndicesStatsRequestBuilder builder, boolean set) {
         switch(flag) {
         case Docs: