diff --git a/Casks/mudlet.rb b/Casks/mudlet.rb
index 49f0fa1d5ad..e33b267b2df 100644
--- a/Casks/mudlet.rb
+++ b/Casks/mudlet.rb
@@ -7,5 +7,7 @@ cask 'mudlet' do
   name 'Mudlet'
   homepage 'https://www.mudlet.org/'
 
+  depends_on macos: '>= :sierra'
+
   app 'Mudlet.app'
 end