diff --git a/requirements_dev.txt b/requirements_dev.txt
index 1ba26e1..60e0de8 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -10,3 +10,4 @@ twine==1.10.0
 
 pytest==3.4.2
 pytest-runner==2.11.1
+urllib3>=2.5.0 # not directly required, pinned by Snyk to avoid a vulnerability