diff --git a/core/src/main/java/org/elasticsearch/tribe/TribeService.java b/core/src/main/java/org/elasticsearch/tribe/TribeService.java
index 06d0fffd75e..f8d2ceb56d0 100644
--- a/core/src/main/java/org/elasticsearch/tribe/TribeService.java
+++ b/core/src/main/java/org/elasticsearch/tribe/TribeService.java
@@ -142,7 +142,7 @@ public class TribeService extends AbstractLifecycleComponent {
      *
      * @param <T> type of custom meta data
      */
-    interface MergableCustomMetaData<T extends MetaData.Custom> {
+    public interface MergableCustomMetaData<T extends MetaData.Custom> {
 
         /**
          * Merges this custom metadata with other, returning either this or <code>other</code> custom metadata