diff --git a/tox.ini b/tox.ini
index b977de05..35096b4d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,7 +17,7 @@ deps =
      cov: coverage
      codecov: codecov
 
-passenv = CI GITHUB_* CODECOV_*
+passenv = CI,GITHUB_*,CODECOV_*
 extras = config
 
 # Run testsuite with coverage when '-cov' is in the env name