--- gtk2/ext/gtk2/extconf.rb.orig
+++ gtk2/ext/gtk2/extconf.rb
@@ -4,6 +4,9 @@
 
 require 'pathname'
 
+Encoding.default_external = Encoding::UTF_8
+Encoding.default_internal = Encoding::UTF_8
+
 source_dir = Pathname(__FILE__).dirname
 base_dir = source_dir.parent.parent.expand_path
 top_dir = base_dir.parent.expand_path

.