diff --git a/travis-textract-requirements/python.txt b/travis-textract-requirements/python.txt
index 98fb9b0..3a43ca9 100644
--- a/travis-textract-requirements/python.txt
+++ b/travis-textract-requirements/python.txt
@@ -12,5 +12,5 @@ xlrd==1.0.0
 EbookLib==0.16
 SpeechRecognition==3.7.1
 https://github.com/mattgwwalker/msg-extractor/zipball/master
-six==1.10.0
+six>=1.11,<2.0
 pocketsphinx==0.1.3