diff --git a/requirements.txt b/requirements.txt
index 108f3a9..f22820b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ inflection==0.5.1
 jsonschema==2.3.0
 pandocfilters==1.2
 six>=1.5.2
+zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability