diff --git a/tests_requirements.txt b/tests_requirements.txt
index 1f20f05..7941d88 100644
--- a/tests_requirements.txt
+++ b/tests_requirements.txt
@@ -1,6 +1,7 @@
 mock==1.1.2
 nose
 nosexcover
+flake8
 
 # Seems that mock doesn't list this one
 funcsigs