diff --git a/dev-requirements.txt b/dev-requirements.txt
index 1b20fca..d45def7 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -1,3 +1,4 @@
+PyYAML==3.13
 coverage==4.5.1
 mock==2.0.0
 nose==1.3.7