diff --git a/requirements.txt b/requirements.txt
index 2b4c019..5bfa274 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -19,3 +19,4 @@ six>=1.16.0
 tomli>=1.2.2
 wheel>=0.37.0
 XlsxWriter>=3.0.2
+fonttools>=4.43.0 # not directly required, pinned by Snyk to avoid a vulnerability