diff --git a/python/requirements.txt b/python/requirements.txt
index 433b2194701..7316d105814 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -16,7 +16,7 @@ pyflakes == 0.8.1
 
 # For buildbot checking
 voluptuous == 0.10.5
-PyYAML == 3.12
+PyYAML == 4.2b1
 
 # For test-webidl
 ply == 3.8