diff --git a/dev-requirements.txt b/dev-requirements.txt
index 7e1631d6..14546e0b 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -14,8 +14,11 @@ build>=0.5.0
 pep517>=0.9.1
 
 # Safety CI by pyup.io
-safety>=2.2.0
-dparse>=0.6.2
+# Safety is run only on Python >=3.6
+# Safety 2.3.5 (running only on Python >=3.6) requires packaging<22.0,>=21.0, but safety 2.3.4 does not
+#   and safety 2.4.0 will also no longer pin it (see https://github.com/pyupio/safety/issues/455).
+safety>=2.2.0,!=2.3.5; python_version >= '3.6'
+dparse>=0.6.2; python_version >= '3.6'
 ruamel.yaml>=0.17.21,<0.17.22; python_version == '3.6'
 ruamel.yaml>=0.17.21; python_version >= '3.7'