jmcnamara is right, of course. If I may venture some further explanation: Remember that character classes and ranges, like a-z and \s, represent any of a number of characters, and are only used in the "find" rather than the "replace" part of a regex. It's impossible to use \s in a replacement because \s could be any one of a space, \t, \n, \r, or \f. As jmcnamara demonstrated, you need to specify the exact character you want to use as the replacement.