diff --git a/requirements.txt b/requirements.txt
index 7ce4516..e75cd62 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -32,3 +32,4 @@ bokeh
 Flask==0.10.1
 PyTrie==0.2
 requests
+pillow>=8.3.0 # not directly required, pinned by Snyk to avoid a vulnerability