diff --git a/dev-requirements.txt b/dev-requirements.txt
index 62e971c..d1484b2 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -4,3 +4,4 @@ colour>=0.0.5
 mock>=1.0
 pep8>=1.5.7
 google-api-python-client>=1.4.2
+python-dateutil>=2.4.2