diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/MockMustacheScriptEngine.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/MockMustacheScriptEngine.java
index a1fd6ca0fa2..0ffebd20223 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/MockMustacheScriptEngine.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/MockMustacheScriptEngine.java
@@ -41,8 +41,8 @@ public class MockMustacheScriptEngine extends MockScriptEngine {
     }
 
     @Override
-    public List<String> getExtensions() {
-        return Collections.singletonList(NAME);
+    public String getExtension() {
+        return NAME;
     }
 
     @Override
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/SleepScriptEngine.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/SleepScriptEngine.java
index c79ebec978a..54e5512e551 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/SleepScriptEngine.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/script/SleepScriptEngine.java
@@ -22,8 +22,6 @@ public class SleepScriptEngine implements ScriptEngineService {
 
     public static final String NAME = "sleep";
 
-    public static final List<String> TYPES = Collections.singletonList(NAME);
-
     public static class TestPlugin extends Plugin {
 
         public TestPlugin() {
@@ -52,8 +50,8 @@ public class SleepScriptEngine implements ScriptEngineService {
     }
 
     @Override
-    public List<String> getExtensions() {
-        return TYPES;
+    public String getExtension() {
+        return NAME;
     }
 
     @Override