Issue #1157 has been updated by Lutz Mueller. my apologies if this is obvious, but I struggled with the same problem. gem update fails in a similar manner. I downloaded the zlib sources from www.zlib.net, went through configure/make/make install. I then went back to the ruby 1.9.1 source directory and also repeated the configure/make/make install. Afterwards, I was able to do a "gem update" and a "gem install rails". I am posting this here because this happened to be the first place I hit in search for a solution. FWIW, Michael Lang's solution (above) did not work for me. I am running Ubuntu 8.10 Intrepid. Regards, Lutz ---------------------------------------- http://redmine.ruby-lang.org/issues/show/1157 ---------------------------------------- http://redmine.ruby-lang.org