diff --git a/lib/mruby/build/command.rb b/lib/mruby/build/command.rb
index 31a595ef0..c8a3037ee 100644
--- a/lib/mruby/build/command.rb
+++ b/lib/mruby/build/command.rb
@@ -25,11 +25,7 @@ module MRuby
     end
 
     def shellquote(s)
-      if ENV['OS'] == 'Windows_NT'
-        "\"#{s}\""
-      else
-        "#{s}"
-      end
+      "\"#{s}\""
     end
 
     private