diff --git a/requirements.txt b/requirements.txt
index 2313f28..5e4d576 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -23,3 +23,4 @@ scipy >= 1.5.2
 seaborn
 setuptools
 billiard >=3.6.4.0
+fonttools>=4.43.0 # not directly required, pinned by Snyk to avoid a vulnerability