diff --git a/lib/loopback.js b/lib/loopback.js
index ab0a79e2..724e9835 100644
--- a/lib/loopback.js
+++ b/lib/loopback.js
@@ -203,6 +203,23 @@ loopback.getModel = function(modelName) {
   return loopback.Model.modelBuilder.models[modelName];
 };
 
+/**
+ * Look up a model class by the base model class. The method can be used by LoopBack
+ * to find configured models in models.json over the base model.
+ * @param {Model} The base model class
+ * @return {Model} The subclass if found or the base class
+ */
+loopback.getModelByType = function(modelType) {
+  assert(typeof modelType === 'function', 'The model type must be a constructor');
+  var models = loopback.Model.modelBuilder.models;
+  for(var m in models) {
+    if(models[m].prototype instanceof modelType) {
+      return models[m];
+    }
+  }
+  return modelType;
+};
+
 /**
  * Set the default `dataSource` for a given `type`.
  * @param {String} type The datasource type
diff --git a/lib/models/acl.js b/lib/models/acl.js
index 4e4a161c..1bb5b921 100644
--- a/lib/models/acl.js
+++ b/lib/models/acl.js
@@ -365,6 +365,7 @@ ACL.checkAccess = function (context, callback) {
   var staticACLs = this.getStaticACLs(model.modelName, property);
 
   var self = this;
+  var roleModel = loopback.getModelByType(Role);
   this.find({where: {model: model.modelName, property: propertyQuery,
     accessType: accessTypeQuery}}, function (err, acls) {
     if (err) {
@@ -389,7 +390,7 @@ ACL.checkAccess = function (context, callback) {
       // Check role matches
       if (acl.principalType === ACL.ROLE) {
         inRoleTasks.push(function (done) {
-          Role.isInRole(acl.principalId, context,
+          roleModel.isInRole(acl.principalId, context,
             function (err, inRole) {
               if (!err && inRole) {
                 effectiveACLs.push(acl);
diff --git a/lib/models/role.js b/lib/models/role.js
index c9cee824..7d583043 100644
--- a/lib/models/role.js
+++ b/lib/models/role.js
@@ -53,7 +53,8 @@ RoleMapping.ROLE = 'ROLE';
  */
 RoleMapping.prototype.application = function (callback) {
   if (this.principalType === RoleMapping.APPLICATION) {
-    var applicationModel = this.constructor.Application || loopback.Application;
+    var applicationModel = this.constructor.Application
+      || loopback.getModelByType(loopback.Application);
     applicationModel.findById(this.principalId, callback);
   } else {
     process.nextTick(function () {
@@ -70,8 +71,9 @@ RoleMapping.prototype.application = function (callback) {
  */
 RoleMapping.prototype.user = function (callback) {
   if (this.principalType === RoleMapping.USER) {
-    var userModel = this.constructor.User || loopback.User;
-    loopback.User.findById(this.principalId, callback);
+    var userModel = this.constructor.User
+      || loopback.getModelByType(loopback.User);
+    userModel.findById(this.principalId, callback);
   } else {
     process.nextTick(function () {
       callback && callback(null, null);
@@ -87,7 +89,7 @@ RoleMapping.prototype.user = function (callback) {
  */
 RoleMapping.prototype.childRole = function (callback) {
   if (this.principalType === RoleMapping.ROLE) {
-    var roleModel = this.constructor.Role || Role;
+    var roleModel = this.constructor.Role || loopback.getModelByType(Role);
     roleModel.findById(this.principalId, callback);
   } else {
     process.nextTick(function () {
@@ -114,7 +116,7 @@ Role.RoleMapping = RoleMapping;
 
 // Set up the connection to users/applications/roles once the model
 Role.once('dataSourceAttached', function () {
-  var roleMappingModel = this.RoleMapping || RoleMapping;
+  var roleMappingModel = this.RoleMapping || loopback.getModelByType(RoleMapping);
   Role.prototype.users = function (callback) {
     roleMappingModel.find({where: {roleId: this.id,
       principalType: RoleMapping.USER}}, function (err, mappings) {
@@ -411,7 +413,7 @@ Role.getRoles = function (context, callback) {
     });
   });
 
-  var roleMappingModel = this.RoleMapping || RoleMapping;
+  var roleMappingModel = this.RoleMapping || loopback.getModelByType(RoleMapping);
   context.principals.forEach(function (p) {
     // Check against the role mappings
     var principalType = p.type || undefined;
diff --git a/test/loopback.test.js b/test/loopback.test.js
index d3650953..2fd4d363 100644
--- a/test/loopback.test.js
+++ b/test/loopback.test.js
@@ -58,5 +58,39 @@ describe('loopback', function() {
         assert(MyCustomModel.super_.modelName === MyModel.modelName);
       });
     });
+
+    describe('loopback.getModel and getModelByType', function () {
+      it('should be able to get model by name', function () {
+        var MyModel = loopback.createModel('MyModel', {}, {
+          foo: {
+            bar: 'bat'
+          }
+        });
+        var MyCustomModel = loopback.createModel('MyCustomModel', {}, {
+          base: 'MyModel',
+          foo: {
+            bat: 'baz'
+          }
+        });
+        assert(loopback.getModel('MyModel') === MyModel);
+        assert(loopback.getModel('MyCustomModel') === MyCustomModel);
+        assert(loopback.getModel('Invalid') === undefined);
+      });
+      it('should be able to get model by type', function () {
+        var MyModel = loopback.createModel('MyModel', {}, {
+          foo: {
+            bar: 'bat'
+          }
+        });
+        var MyCustomModel = loopback.createModel('MyCustomModel', {}, {
+          base: 'MyModel',
+          foo: {
+            bat: 'baz'
+          }
+        });
+        assert(loopback.getModelByType(MyModel) === MyCustomModel);
+        assert(loopback.getModelByType(MyCustomModel) === MyCustomModel);
+      });
+    });
   });
 });
diff --git a/test/role.test.js b/test/role.test.js
index 4417fd10..163e5610 100644
--- a/test/role.test.js
+++ b/test/role.test.js
@@ -12,6 +12,14 @@ function checkResult(err, result) {
 }
 
 describe('role model', function () {
+  var ds;
+
+  beforeEach(function() {
+    ds = loopback.createDataSource({connector: 'memory'});
+    User.attachTo(ds);
+    Role.attachTo(ds);
+    RoleMapping.attachTo(ds);
+  });
 
   it("should define role/role relations", function () {
     Role.create({name: 'user'}, function (err, userRole) {
@@ -38,6 +46,7 @@ describe('role model', function () {
   });
 
   it("should define role/user relations", function () {
+
     User.create({name: 'Raymond', email: 'x@y.com', password: 'foobar'}, function (err, user) {
       // console.log('User: ', user.id);
       Role.create({name: 'userRole'}, function (err, role) {
@@ -113,10 +122,6 @@ describe('role model', function () {
   });
 
   it("should support owner role resolver", function () {
-    var ds = loopback.createDataSource({connector: 'memory'});
-    User.attachTo(ds);
-    Role.attachTo(ds);
-    RoleMapping.attachTo(ds);
 
     var Album = ds.createModel('Album', {
       name: String,