diff --git a/Casks/z/zenmap.rb b/Casks/z/zenmap.rb
index 1f1bb1da9a..c886634067 100644
--- a/Casks/z/zenmap.rb
+++ b/Casks/z/zenmap.rb
@@ -12,6 +12,8 @@ cask "zenmap" do
     regex(/href=.*?nmap[._-]v?(\d+(?:\.\d+)+)\.dmg/i)
   end
 
+  conflicts_with formula: "nmap"
+
   pkg "nmap-#{version}.mpkg"
 
   uninstall delete:  "/Applications/Zenmap.app",