diff --git a/requirements.txt b/requirements.txt
index 30320fb2b..1870b8ecb 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,7 +12,7 @@ multidict==3.3.2
 mypy==0.550
 packaging==16.8
 pycodestyle==2.3.1
-py==1.5.0
+py==1.4.34
 pyparsing==2.2.0
 pytest==3.2.4
 pytest-cov==2.5.1