diff --git a/src/main/java/org/elasticsearch/index/engine/Engine.java b/src/main/java/org/elasticsearch/index/engine/Engine.java
index 5f0d8144069..1131a5bff29 100644
--- a/src/main/java/org/elasticsearch/index/engine/Engine.java
+++ b/src/main/java/org/elasticsearch/index/engine/Engine.java
@@ -182,7 +182,7 @@ public interface Engine extends IndexShardComponent, CloseableComponent {
 
         @Override
         public String source() {
-            return this.source();
+            return source;
         }
 
         @Override