diff --git a/colab_requirements.txt b/colab_requirements.txt
index ad064135a12..6b90c25c221 100644
--- a/colab_requirements.txt
+++ b/colab_requirements.txt
@@ -1,2 +1,3 @@
 matplotlib
 jupyter
+tornado>=6.4.2 # not directly required, pinned by Snyk to avoid a vulnerability