diff --git a/tox.ini b/tox.ini
index cea30da..7bef4da 100644
--- a/tox.ini
+++ b/tox.ini
@@ -20,6 +20,7 @@ skip_missing_interpreters = True
 deps =
     pyflakes >= 1.2.3
     mock
+usedevelop=true
 install_command = pip install {packages}
 commands =
     pyflakes setup.py src
@@ -39,6 +40,7 @@ deps =
     pyflakes >= 1.2.3
     mock
     coverage
+usedevelop=true
 install_command = pip install {packages}
 commands =
     pyflakes setup.py src