diff --git a/css/requirements.txt b/css/requirements.txt
index b6772bcd162716..2e8802531ef4f2 100644
--- a/css/requirements.txt
+++ b/css/requirements.txt
@@ -1,6 +1,6 @@
 Template-Python==0.1.post1
 html5lib==1.1
 lxml==4.6.3
-mercurial==4.6.1
+mercurial==5.9.3
 six==1.15.0
 webencodings==0.5.1