diff --git a/requirements.txt b/requirements.txt
index 18127973..18fa2ec6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -22,6 +22,7 @@ boto==2.36.0
 elasticsearch==1.2.0
 itsdangerous==0.24
 requests== 2.22.0
+six==1.12.0
 urllib3==1.24.2
 dicttoxml==1.5.8
 sqlalchemy==1.3.5