diff --git a/Library/Homebrew/cask/lib/hbc/cli/install.rb b/Library/Homebrew/cask/lib/hbc/cli/install.rb
index 9a2116e6ac..d8f148b1ba 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/install.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/install.rb
@@ -10,6 +10,7 @@ module Hbc
       end
 
       def run
+        odie "Installing casks is supported only on macOS" unless OS.mac?
         casks.each do |cask|
           begin
             Installer.new(cask, binaries:       binaries?,