diff --git a/tox.ini b/tox.ini
index b79588f287..da58ec017b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,12 +9,16 @@ install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt
        .[ldap,memcache,mongodb]
-commands = bash tools/pretty_tox.sh '{posargs}'
+commands =
+  find keystone -type f -name "*.pyc" -delete
+  bash tools/pretty_tox.sh '{posargs}'
 whitelist_externals = bash
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY PBR_VERSION
 
 [testenv:py34]
-commands = bash tools/pretty_tox_py3.sh
+commands =
+  find keystone -type f -name "*.pyc" -delete
+  bash tools/pretty_tox_py3.sh
 
 [testenv:legacy_drivers]
 deps = -r{toxinidir}/test-requirements.txt
@@ -22,6 +26,7 @@ deps = -r{toxinidir}/test-requirements.txt
        .[ldap,memcache,mongodb]
 commands =
   # Run each legacy test separately, to avoid SQL model redefinitions
+  find keystone -type f -name "*.pyc" -delete
   nosetests -v \
       keystone/tests/unit/backend/legacy_drivers/assignment/V8/sql.py
   nosetests -v \
@@ -53,13 +58,17 @@ deps = .[bandit]
 commands = bandit -r keystone
 
 [testenv:cover]
-commands = python setup.py testr --coverage --testr-args='{posargs}'
+commands =
+  find keystone -type f -name "*.pyc" -delete
+  python setup.py testr --coverage --testr-args='{posargs}'
 
 [testenv:venv]
 commands = {posargs}
 
 [testenv:debug]
-commands = oslo_debug_helper {posargs}
+commands =
+  find keystone -type f -name "*.pyc" -delete
+  oslo_debug_helper {posargs}
 passenv =
     KSTEST_ADMIN_URL
     KSTEST_ADMIN_USERNAME
@@ -75,7 +84,9 @@ passenv =
 basepython = python3.4
 deps = -r{toxinidir}/test-requirements.txt
 setenv = OS_TEST_PATH=./keystone/tests/functional
-commands = python setup.py testr --slowest --testr-args='{posargs}'
+commands =
+  find keystone -type f -name "*.pyc" -delete
+  python setup.py testr --slowest --testr-args='{posargs}'
 passenv =
     KSTEST_ADMIN_URL
     KSTEST_ADMIN_USERNAME