diff --git a/Rakefile b/Rakefile
index 199959c..6744120 100644
--- a/Rakefile
+++ b/Rakefile
@@ -302,7 +302,7 @@ def install_prezto
   run %{ mkdir -p $HOME/.zsh.after }
   run %{ mkdir -p $HOME/.zsh.prompts }
 
-  if ENV["SHELL"].include? 'zsh' then
+  if "#{ENV['SHELL']}".include? 'zsh' then
     puts "Zsh is already configured as your shell of choice. Restart your session to load the new settings"
   else
     puts "Setting zsh as your default shell"