diff --git a/tox.ini b/tox.ini
index acd7dd33b4..3fb454e734 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,10 +7,13 @@ skipsdist = True
 usedevelop = True
 setenv = VIRTUAL_ENV={envdir}
 install_command = pip install -U {opts} {packages}
+whitelist_externals = find
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
        -r{toxinidir}/doc-requirements.txt
-commands = python setup.py testr --slowest --testr-args='{posargs}'
+commands =
+  find . -type f -name "*.pyc" -delete
+  python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:cover]
 commands = python setup.py testr --coverage --testr-args='{posargs}'