diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -31,4 +31,5 @@ txzmq==0.7.4
 pyusb==1.0.0
 coverage==4.1
 klein==15.3.1
-git+http://github.com/drewp/scales.git@448d59fb491b7631877528e7695a93553bfaaa93#egg=scales
\ No newline at end of file
+git+http://github.com/drewp/scales.git@448d59fb491b7631877528e7695a93553bfaaa93#egg=scales
+colormath==2.1.1