diff --git a/groovy/src/main/java/org/apache/zeppelin/groovy/GroovyInterpreter.java b/groovy/src/main/java/org/apache/zeppelin/groovy/GroovyInterpreter.java
index b8eef8c342e..3c6cbed8740 100644
--- a/groovy/src/main/java/org/apache/zeppelin/groovy/GroovyInterpreter.java
+++ b/groovy/src/main/java/org/apache/zeppelin/groovy/GroovyInterpreter.java
@@ -117,7 +117,7 @@ private Job getRunningJob(String paragraphId) {
   @Override
   public List<InterpreterCompletion> completion(String buf, int cursor,
                                                 InterpreterContext interpreterContext) {
-    return null;
+    return Collections.emptyList();
   }
 
   @SuppressWarnings("unchecked")