diff --git a/lib/adapters/http.js b/lib/adapters/http.js
index 73dc26e..d6908b3 100644
--- a/lib/adapters/http.js
+++ b/lib/adapters/http.js
@@ -55,6 +55,8 @@ module.exports = function httpAdapter(config) {
 
     // Parse url
     var parsed = url.parse(config.url);
+    var protocol = parsed.protocol || 'http:';
+
     if (!auth && parsed.auth) {
       var urlAuth = parsed.auth.split(':');
       var urlUsername = urlAuth[0] || '';
@@ -66,7 +68,7 @@ module.exports = function httpAdapter(config) {
       delete headers.Authorization;
     }
 
-    var isHttps = parsed.protocol === 'https:';
+    var isHttps = protocol === 'https:';
     var agent = isHttps ? config.httpsAgent : config.httpAgent;
 
     var options = {
@@ -81,7 +83,7 @@ module.exports = function httpAdapter(config) {
 
     var proxy = config.proxy;
     if (!proxy) {
-      var proxyEnv = parsed.protocol.slice(0, -1) + '_proxy';
+      var proxyEnv = protocol.slice(0, -1) + '_proxy';
       var proxyUrl = process.env[proxyEnv] || process.env[proxyEnv.toUpperCase()];
       if (proxyUrl) {
         var parsedProxyUrl = url.parse(proxyUrl);
@@ -97,7 +99,7 @@ module.exports = function httpAdapter(config) {
       options.hostname = proxy.host;
       options.headers.host = parsed.hostname + (parsed.port ? ':' + parsed.port : '');
       options.port = proxy.port;
-      options.path = parsed.protocol + '//' + parsed.hostname + (parsed.port ? ':' + parsed.port : '') + options.path;
+      options.path = protocol + '//' + parsed.hostname + (parsed.port ? ':' + parsed.port : '') + options.path;
     }
 
     var transport;