diff --git a/tox.ini b/tox.ini
index 20bffca0..36e16846 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,10 @@ setenv = VIRTUAL_ENV={envdir}
          ZAQAR_TEST_SLOW=1
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = python setup.py testr --slowest --testr-args='--concurrency 1 {posargs}'
+commands =
+    find . -type f -name "*.pyc" -delete
+    python setup.py testr --slowest --testr-args='--concurrency 1 {posargs}'
+whitelist_externals = find
 
 [testenv:pypy]
 setenv = {[testenv]setenv}