diff --git a/src/config.js b/src/config.js
index 6cad2178..99256696 100644
--- a/src/config.js
+++ b/src/config.js
@@ -147,12 +147,12 @@ export function setConfig (cfg, isEnvConfig) {
       var v = cfg.map[p];
 
       if (typeof v === 'string') {
-        config.map[p] = coreResolve.call(loader, config, v, undefined, false);
+        config.map[p] = coreResolve.call(loader, config, v, undefined, false, false);
       }
 
       // object map
       else {
-        var pkgName = coreResolve.call(loader, config, p, undefined, true);
+        var pkgName = coreResolve.call(loader, config, p, undefined, true, true);
         var pkg = config.packages[pkgName];
         if (!pkg) {
           pkg = config.packages[pkgName] = createPackage();
@@ -169,7 +169,7 @@ export function setConfig (cfg, isEnvConfig) {
     for (var i = 0; i < cfg.packageConfigPaths.length; i++) {
       var path = cfg.packageConfigPaths[i];
       var packageLength = Math.max(path.lastIndexOf('*') + 1, path.lastIndexOf('/'));
-      var normalized = coreResolve.call(loader, config, path.substr(0, packageLength), undefined, false);
+      var normalized = coreResolve.call(loader, config, path.substr(0, packageLength), undefined, false, false);
       packageConfigPaths[i] = normalized + path.substr(packageLength);
     }
     config.packageConfigPaths = packageConfigPaths;
@@ -189,8 +189,7 @@ export function setConfig (cfg, isEnvConfig) {
       if (p.match(/^([^\/]+:)?\/\/$/))
         throw new TypeError('"' + p + '" is not a valid package name.');
 
-      var pkgName = coreResolve.call(loader, config, p[p.length -1] !== '/' ? p + '/' : p, undefined, true);
-      pkgName = pkgName.substr(0, pkgName.length - 1);
+      var pkgName = coreResolve.call(loader, config, p, undefined, true, true);
 
       setPkgConfig(config.packages[pkgName] = config.packages[pkgName] || createPackage(), cfg.packages[p], pkgName, false, config);
     }
@@ -208,7 +207,7 @@ export function setConfig (cfg, isEnvConfig) {
         extend(config.meta[p] = config.meta[p] || {}, cfg.meta[p]);
       }
       else {
-        var resolved = coreResolve.call(loader, config, p, undefined, true);
+        var resolved = coreResolve.call(loader, config, p, undefined, true, true);
         extend(config.meta[resolved] = config.meta[resolved] || {}, cfg.meta[p]);
       }
     }
diff --git a/src/resolve.js b/src/resolve.js
index 158ef0a4..702eab41 100644
--- a/src/resolve.js
+++ b/src/resolve.js
@@ -152,10 +152,10 @@ export function decanonicalize (config, key) {
   // plugin
   if (parsed) {
     var pluginKey = decanonicalize.call(this, config, parsed.plugin);
-    return combinePluginParts(config.pluginFirst, coreResolve.call(this, config, parsed.argument, undefined, false), pluginKey);
+    return combinePluginParts(config.pluginFirst, coreResolve.call(this, config, parsed.argument, undefined, false, false), pluginKey);
   }
 
-  return coreResolve.call(this, config, key, undefined, false);
+  return coreResolve.call(this, config, key, undefined, false, false);
 }
 
 export function normalizeSync (key, parentKey) {
@@ -178,7 +178,7 @@ export function normalizeSync (key, parentKey) {
   return packageResolveSync.call(this, config, key, parentMetadata.pluginArgument || parentKey, metadata, parentMetadata, !!metadata.pluginKey);
 }
 
-export function coreResolve (config, key, parentKey, doMap) {
+export function coreResolve (config, key, parentKey, doMap, packageName) {
   var relativeResolved = resolveIfNotPlain(key, parentKey || baseURI);
 
   // standard URL resolution
@@ -204,7 +204,11 @@ export function coreResolve (config, key, parentKey, doMap) {
   if (key.substr(0, 6) === '@node/')
     return key;
 
-  return applyPaths(config.baseURL, config.paths, key);
+  var trailingSlash = packageName && key[key.length - 1] !== '/';
+  var resolved = applyPaths(config.baseURL, config.paths, trailingSlash ? key + '/' : key);
+  if (trailingSlash)
+    return resolved.substr(0, resolved.length - 1);
+  return resolved;
 }
 
 function packageResolveSync (config, key, parentKey, metadata, parentMetadata, skipExtensions) {
@@ -220,7 +224,10 @@ function packageResolveSync (config, key, parentKey, metadata, parentMetadata, s
     }
   }
 
-  var normalized = coreResolve.call(this, config, key, parentKey, true);
+  var trailingSlash = key[key.length - 1] === '/';
+  var normalized = coreResolve.call(this, config, trailingSlash ? key : key + '/', parentKey, true, true);
+  if (!trailingSlash)
+    normalized = normalized.substr(0, normalized.length - 1);
 
   var pkgConfigMatch = getPackageConfigMatch(config, normalized);
   metadata.packageKey = pkgConfigMatch && pkgConfigMatch.packageKey || getMapMatch(config.packages, normalized);
@@ -261,7 +268,7 @@ function packageResolve (config, key, parentKey, metadata, parentMetadata, skipE
       return mapped;
 
     // apply map, core, paths, contextual package map
-    var normalized = coreResolve.call(loader, config, key, parentKey, true);
+    var normalized = coreResolve.call(loader, config, key, parentKey, true, true);
 
     var pkgConfigMatch = getPackageConfigMatch(config, normalized);
     metadata.packageKey = pkgConfigMatch && pkgConfigMatch.packageKey || getMapMatch(config.packages, normalized);
diff --git a/test/test.js b/test/test.js
index 1071d397..23cfa25e 100644
--- a/test/test.js
+++ b/test/test.js
@@ -234,7 +234,7 @@ suite('SystemJS Standard Tests', function() {
       }
     });
 
-    var base = System.resolveSync('');
+    var base = System.resolveSync('./');
 
     return Promise.all([
       System.resolve('a'),
@@ -250,7 +250,7 @@ suite('SystemJS Standard Tests', function() {
       ok(a[1] === base + 'c/b');
       ok(a[2] === base + 'b/b');
       ok(a[3] === base + 'd/c');
-      ok(a[4] === base + 'b');
+      ok(a[4] === base + 'd');
       ok(a[5] === 'http://jquery.com/jquery.js');
       ok(a[6] === 'http://jquery.com/jquery.js/c');
       ok(a[7] === 'https://another.com/x');
@@ -1123,6 +1123,24 @@ suite('SystemJS Standard Tests', function() {
     })
   });
 
+  test('Package configuration main normalization', function () {
+    SystemJS.config({
+      paths: {
+        "npm:": "jspm_packages/npm/",
+        "app/": "src/"
+      },
+      packages: {
+        "app": {
+          "format": "system",
+          "main": "index.js"
+        }
+      }
+    });
+
+    console.log(System.normalizeSync('app'));
+    ok(System.normalizeSync('app') === System.baseURL + 'src/index.js');
+  });
+
   test('esModule meta option', function () {
     System.config({
       meta: {