diff --git a/testrequirements.txt b/testrequirements.txt
index e465d4ca..8ac33c19 100644
--- a/testrequirements.txt
+++ b/testrequirements.txt
@@ -2,6 +2,7 @@ appdirs~=1.4.0
 coverage
 mock
 pyftpdlib==1.5.2
+PyYAML<4.1          ;   python_version == '3.3'
 python-coveralls
 pytz==2016.7
 nose