When the HTTP adapter is used, it goes down a different code path, so the undocumented _implicitHeader function is missing from http.ServerResponse.

This causes some very common code (the Expressjs "compress" middleware) to fail because those guys just love to depend on undocumented stuff. Yay Node.

The following monkey-patch, which can go anywhere as long as it's before the first HTTP response, helps:

var http = require('http');
http.ServerResponse.prototype._implicitHeader = function() {
this.writeHead(this.statusCode);
};