diff --git a/tools/pip-requires b/tools/pip-requires
index 1060acc..49ab0ed 100644
--- a/tools/pip-requires
+++ b/tools/pip-requires
@@ -8,4 +8,4 @@
 python-daemon
 extras
 statsd==1.0.0
-voluptuous>=0.6
+voluptuous>=0.6,<0.7