diff --git a/lib/datasource.js b/lib/datasource.js
index 9602ec4f..fefe10a2 100644
--- a/lib/datasource.js
+++ b/lib/datasource.js
@@ -14,6 +14,7 @@ var util = require('util');
 var assert = require('assert');
 var async = require('async');
 var traverse = require('traverse');
+var i8n = require('inflection');
 
 if (process.env.DEBUG === 'loopback') {
   // For back-compatibility
@@ -429,19 +430,39 @@ DataSource.prototype.defineRelations = function (modelClass, relations) {
     for (var rn in relations) {
       var r = relations[rn];
       assert(DataSource.relationTypes.indexOf(r.type) !== -1, "Invalid relation type: " + r.type);
-      var targetModel = isModelClass(r.model) ? r.model : this.getModel(r.model, true);
+      var targetModel, polymorphicName;
+      
+      if (r.polymorphic && r.type !== 'belongsTo' && !r.model) {
+        throw new Error('No model specified for polymorphic ' + r.type + ': ' + rn);
+      }
+      
+      if (r.polymorphic) {
+        polymorphicName = typeof r.model === 'string' ? r.model : rn;
+        if (typeof r.polymorphic === 'string') {
+          polymorphicName = r.polymorphic;
+        } else if (typeof r.polymorphic === 'object' && typeof r.polymorphic.as === 'string') {
+          polymorphicName = r.polymorphic.as;
+        }
+      }
+      
+      if (r.model) {
+        targetModel = isModelClass(r.model) ? r.model : this.getModel(r.model, true);
+      }
+      
       var throughModel = null;
       if (r.through) {
         throughModel = isModelClass(r.through) ? r.through : this.getModel(r.through, true);
       }
-      if ((!r.polymorphic && !isModelDataSourceAttached(targetModel)) || (throughModel && !isModelDataSourceAttached(throughModel))) {
+      
+      if ((targetModel && !isModelDataSourceAttached(targetModel)) 
+        || (throughModel && !isModelDataSourceAttached(throughModel))) {
         // Create a listener to defer the relation set up
         createListener(rn, r, targetModel, throughModel);
       } else {
         // The target model is resolved
         var params = traverse(r).clone();
         params.as = rn;
-        params.model = targetModel;
+        params.model = polymorphicName || targetModel;
         if (throughModel) {
           params.through = throughModel;
         }
diff --git a/lib/relation-definition.js b/lib/relation-definition.js
index e11b28bc..c1b51ddb 100644
--- a/lib/relation-definition.js
+++ b/lib/relation-definition.js
@@ -115,12 +115,19 @@ function RelationDefinition(definition) {
 }
 
 RelationDefinition.prototype.toJSON = function () {
+  var polymorphic = typeof this.polymorphic === 'object';
+    
+  var modelToName = this.modelTo && this.modelTo.modelName;
+  if (!modelToName && polymorphic && this.type === 'belongsTo') {
+    modelToName = '<polymorphic>';
+  } 
+    
   var json = {
     name: this.name,
     type: this.type,
     modelFrom: this.modelFrom.modelName,
     keyFrom: this.keyFrom,
-    modelTo: this.modelTo.modelName,
+    modelTo: modelToName,
     keyTo: this.keyTo,
     multiple: this.multiple
   };
@@ -128,6 +135,9 @@ RelationDefinition.prototype.toJSON = function () {
     json.modelThrough = this.modelThrough.modelName;
     json.keyThrough = this.keyThrough;
   }
+  if (polymorphic) {
+    json.polymorphic = this.polymorphic;
+  }
   return json;
 };
 
@@ -449,14 +459,20 @@ function lookupModel(models, modelName) {
 
 function lookupModelTo(modelFrom, modelTo, params, singularize) {
   if ('string' === typeof modelTo) {
+    var modelToName;
     params.as = params.as || modelTo;
     modelTo = params.model || modelTo;
     if (typeof modelTo === 'string') {
-      var modelToName = (singularize ? i8n.singularize(modelTo) : modelTo).toLowerCase();
+      modelToName = (singularize ? i8n.singularize(modelTo) : modelTo).toLowerCase();
+      modelTo = lookupModel(modelFrom.dataSource.modelBuilder.models, modelToName) || modelTo;
+    }
+    if (typeof modelTo === 'string') {
+      modelToName = (singularize ? i8n.singularize(params.as) : params.as).toLowerCase();
+      console.log(modelToName)
       modelTo = lookupModel(modelFrom.dataSource.modelBuilder.models, modelToName) || modelTo;
     }
     if (typeof modelTo !== 'function') {
-      throw new Error('Could not find "' + modelTo + '" relation for ' + modelFrom.modelName);
+      throw new Error('Could not find "' + params.as + '" relation for ' + modelFrom.modelName);
     }
   }
   return modelTo;
@@ -510,7 +526,7 @@ RelationDefinition.hasMany = function hasMany(modelFrom, modelTo, params) {
   
   if (params.polymorphic) {
     polymorphic = polymorphicParams(params.polymorphic);
-    polymorphic.invert = !!params.invert;
+    if (params.invert) polymorphic.invert = true;
     discriminator = polymorphic.discriminator;
     if (!params.invert) {
       fk = polymorphic.foreignKey;
@@ -1172,7 +1188,7 @@ BelongsTo.prototype.related = function (refresh, params) {
     self.resetCache(params);
   } else if (typeof params === 'function') { // acts as async getter
     
-    if (discriminator && !modelTo) {
+    if (discriminator) {
       var modelToName = modelInstance[discriminator];
       if (typeof modelToName !== 'string') {
         throw new Error('Polymorphic model not found: `' + discriminator + '` not set');
diff --git a/test/loopback-dl.test.js b/test/loopback-dl.test.js
index 458f91db..9d2d42d2 100644
--- a/test/loopback-dl.test.js
+++ b/test/loopback-dl.test.js
@@ -923,7 +923,51 @@ describe('Load models with relations', function () {
     assert(User.relations['posts']);
     done();
   });
-
+  
+  it('should set up polymorphic relations', function (done) {
+    var ds = new DataSource('memory');
+  
+    var Author = ds.define('Author', {name: String}, {relations: {
+      pictures: {type: 'hasMany', model: 'Picture', polymorphic: 'imageable'}
+    }});
+    var Picture = ds.define('Picture', {name: String}, {relations: {
+      imageable: {type: 'belongsTo', polymorphic: true}
+    }});
+    
+    assert(Author.relations['pictures']);
+    assert.deepEqual(Author.relations['pictures'].toJSON(), {
+      name: 'pictures',
+      type: 'hasMany',
+      modelFrom: 'Author',
+      keyFrom: 'id',
+      modelTo: 'Picture',
+      keyTo: 'imageableId',
+      multiple: true,
+      polymorphic: { 
+        as: 'imageable',
+        foreignKey: 'imageableId',
+        discriminator: 'imageableType'
+      }
+    });
+    
+    assert(Picture.relations['imageable']);
+    assert.deepEqual(Picture.relations['imageable'].toJSON(), {
+      name: 'imageable',
+      type: 'belongsTo',
+      modelFrom: 'Picture',
+      keyFrom: 'imageableId',
+      modelTo: '<polymorphic>',
+      keyTo: 'id',
+      multiple: false,
+      polymorphic: { 
+        as: 'imageable',
+        foreignKey: 'imageableId',
+        discriminator: 'imageableType'
+      }
+    });
+    done();
+  });
+  
   it('should set up foreign key with the correct type', function (done) {
     var ds = new DataSource('memory');
 
diff --git a/test/relations.test.js b/test/relations.test.js
index 87610f84..871ecb54 100644
--- a/test/relations.test.js
+++ b/test/relations.test.js
@@ -686,6 +686,37 @@ describe('relations', function () {
         discriminator: 'imageableType'
       } });
       Picture.belongsTo('imageable', { polymorphic: true });
+      
+      Author.relations['pictures'].toJSON().should.eql({
+        name: 'pictures',
+        type: 'hasMany',
+        modelFrom: 'Author',
+        keyFrom: 'id',
+        modelTo: 'Picture',
+        keyTo: 'imageableId',
+        multiple: true,
+        polymorphic: { 
+          as: 'imageable',
+          foreignKey: 'imageableId',
+          discriminator: 'imageableType'
+        }
+      });
+      
+      Picture.relations['imageable'].toJSON().should.eql({
+        name: 'imageable',
+        type: 'belongsTo',
+        modelFrom: 'Picture',
+        keyFrom: 'imageableId',
+        modelTo: '<polymorphic>',
+        keyTo: 'id',
+        multiple: false,
+        polymorphic: { 
+          as: 'imageable',
+          foreignKey: 'imageableId',
+          discriminator: 'imageableType'
+        }
+      });
+      
       db.automigrate(done);
     });