diff --git a/requirements.txt b/requirements.txt
index 22c0364..fd4f6d2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ numpy>=1.9.3
 matplotlib>=3.1.1
 peakdet
 scipy
+fonttools>=4.43.0 # not directly required, pinned by Snyk to avoid a vulnerability