diff --git a/modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/CustomScoreQueryParser.java b/modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/CustomScoreQueryParser.java
index dd860438f22..cd70ed0f982 100644
--- a/modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/CustomScoreQueryParser.java
+++ b/modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/CustomScoreQueryParser.java
@@ -120,6 +120,7 @@ public class CustomScoreQueryParser extends AbstractIndexComponent implements XC
 
         @Override public float score(int docId, float subQueryScore) {
             vars.put("score", subQueryScore);
+            vars.put("_score", subQueryScore);
             return ((Number) scriptFieldsFunction.execute(docId, vars)).floatValue();
         }