diff --git a/tox.ini b/tox.ini
index bd313a4f36..6f01599af7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,7 +11,7 @@ deps =
 setenv =
     PYTHONDONTWRITEBYTECODE = no_byte_code
 commands =
-    /bin/bash -c "coverage run {env:COVERAGE_OPTS:} --source={toxinidir}/synapse \
+    /bin/bash -c "find {toxinidir} -name '*.pyc' -delete ; coverage run {env:COVERAGE_OPTS:} --source={toxinidir}/synapse \
         {envbindir}/trial {env:TRIAL_FLAGS:} {posargs:tests} {env:TOXSUFFIX:}"
     {env:DUMP_COVERAGE_COMMAND:coverage report -m}