diff --git a/tests/requirements-py3.txt b/tests/requirements-py3.txt
index b425ce771..b51177abb 100644
--- a/tests/requirements-py3.txt
+++ b/tests/requirements-py3.txt
@@ -1,9 +1,9 @@
 # Tests requirements
 attrs
-dataclasses; python_version ==3.6
-mitmproxy; python_version >=3.7
-mitmproxy >=4, <5; python_version >=3.6, <3.7
-mitmproxy <4; python_version <3.6
+dataclasses; python_version == '3.6'
+mitmproxy; python_version >= '3.7'
+mitmproxy >= 4, < 5; python_version >= '3.6' and python_version < '3.7'
+mitmproxy < 4; python_version < '3.6'
 # https://github.com/pytest-dev/pytest-twisted/issues/93
 pytest != 5.4, != 5.4.1
 pytest-azurepipelines