diff --git a/lib/package.js b/lib/package.js
index 969ec4042..893675ff0 100644
--- a/lib/package.js
+++ b/lib/package.js
@@ -286,29 +286,6 @@ function derivePackageConfig(pjson, override) {
   if (override)
     extend(dpjson, override);
 
-  // if there is a "browser" object, convert it into map config for browserify support
-  if (typeof pjson.browser == 'object') {
-    dpjson.map = dpjson.map || {};
-    for (var b in pjson.browser) {
-      var mapping = pjson.browser[b];
-      if (typeof mapping != 'string')
-        continue;
-      if (b.substr(b.length - 3, 3) == '.js')
-        b = b.substr(0, b.length - 3);
-      if (mapping.substr(mapping.length - 3, 3) == '.js')
-        mapping = mapping.substr(0, mapping.length - 3);
-      
-      // local maps not supported since this affects the external
-      // interface for all other modules
-      // only way to implement is through a module alias replacement
-      // may be worth considering at some point
-      if (b.substr(0, 2) == './')
-        continue;
-
-      dpjson.map[b] = dpjson.map[b] || mapping;
-    }
-  }
-
   // finally set the derived package.json as the "jspm" property on the package.json
   return dpjson;
 }
@@ -456,6 +433,7 @@ exports.download = function(pkg, jspmPackages, options, preload) {
 
   .then(function(fresh) {
     // fire off preloading using early getPackageConfig hook if available
+    // NB this can run in parallel to download with Promise.all
     if (endpoint.getPackageConfig)
       // we only use the getPackageConfig pjson if
       // we are going to run a build, otherwise we use the saved one
@@ -595,7 +573,7 @@ exports.createMain = function(pkg, pjson, downloadDir) {
   // create the main entry point
   .then(function() {
     lastNamePart = pkg.name.split('/').pop().split(':').pop();
-    main = typeof pjson.browser == 'string' && pjson.browser || typeof pjson.main == 'string' && pjson.main;
+    main = typeof pjson.main == 'string' && pjson.main;
 
     if (main) {
       if (main.substr(0, 2) == './')