Issue #5433 has been updated by Eric Hodel. On Ruby 1.9.2-p290 compiled with GCC (not LLVM-GCC) OS X 10.7.1 panics when I run your command. ---------------------------------------- Bug #5433: PTY.spawn Kernel panic on macos lion http://redmine.ruby-lang.org/issues/5433 Author: Gamaliel Toro Status: Open Priority: Normal Assignee: Category: Target version: ruby -v: ruby-1.9.2 If you execute a PTY.spawn with a non existing command give a kernel panic. Example require 'pty' PTY.spawn('nonexistent-command') -- http://redmine.ruby-lang.org