diff --git a/dev-requirements.txt b/dev-requirements.txt
index 672e521..0f6956c 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -7,3 +7,4 @@ coverage==4.4
 codecov
 pytest-cov
 
+urllib3>=2.5.0 # not directly required, pinned by Snyk to avoid a vulnerability