diff --git a/mkconfig.rb b/mkconfig.rb
index 02e91ab339..e64490e287 100644
--- a/mkconfig.rb
+++ b/mkconfig.rb
@@ -137,7 +137,7 @@ print <<EOS
     RbConfig::expand(val)
   end
 end
-Config = RbConfig # compatibility for ruby-1.8 and older.
+Config = RbConfig # compatibility for ruby-1.8.4 and older.
 CROSS_COMPILING = nil unless defined? CROSS_COMPILING
 EOS