diff --git a/test-requirements.txt b/test-requirements.txt
index 512c913..8f5c99a 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -2,3 +2,4 @@ flake8==3.3.0
 flake8-pyi==17.3.0
 pytest==3.4.2
 mypy==0.590
+zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability