diff --git a/tox.ini b/tox.ini
index a363e187faa..b6a67fd8529 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,6 +8,7 @@ passenv =
     https_proxy
     http_proxy
     no_proxy
+    COLORTERM
     PERL
     PERL5LIB
     PYTEST_ADDOPTS