diff --git a/pytorch_lightning/trainer/ddp_mixin.py b/pytorch_lightning/trainer/ddp_mixin.py
index ba5deb4c..67821ae9 100644
--- a/pytorch_lightning/trainer/ddp_mixin.py
+++ b/pytorch_lightning/trainer/ddp_mixin.py
@@ -116,6 +116,7 @@ When the script starts again, Lightning will:
 import os
 import re
 import logging
+import warnings
 
 import torch