diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..b9ca117
Binary files /dev/null and b/.DS_Store differ
diff --git a/lib/deserializer.js b/lib/deserializer.js
index feb10a8..c4a18f6 100644
--- a/lib/deserializer.js
+++ b/lib/deserializer.js
@@ -1,6 +1,7 @@
 'use strict'
 
 var _ = require('lodash')
+var utils = require('./utils')
 
 function defaultBeforeDeserialize (options, cb) {
   cb(null, options)
@@ -78,6 +79,20 @@ function belongsToRelationships (options) {
     if (!relationship.data) {
       options.result[fkName] = null
     } else {
+      if (serverRelation.polymorphic) {
+        // Find the model which has a plural matching 'data.type'
+        // Allow case insensitive match
+        var relatedType = relationship.data.type.toLowerCase()
+        var modelName = _.findKey(model.app.models, function (model) {
+          var plural = utils.pluralForModel(model)
+          return plural.toLowerCase() === relatedType
+        })
+        if (!modelName) {
+          return false
+        }
+        var discriminator = serverRelation.polymorphic.discriminator
+        options.result[discriminator] = modelName
+      }
       options.result[fkName] = relationship.data.id
     }
   })
diff --git a/lib/serializer.js b/lib/serializer.js
index 0d355c1..4db9f5f 100644
--- a/lib/serializer.js
+++ b/lib/serializer.js
@@ -233,8 +233,12 @@ function parseRelations (data, relations, options) {
     var toType = ''
     if (relation.polymorphic && utils.relationFkOnModelFrom(relation)) {
       var discriminator = relation.polymorphic.discriminator
-      var model = options.app.models[data[discriminator]]
-      toType = utils.pluralForModel(model)
+      if (data.discriminator) {
+        var model = options.app.models[data[discriminator]]
+        if (model) {
+          toType = utils.pluralForModel(model)
+        }
+      }
     } else {
       toType = utils.pluralForModel(relation.modelTo)
     }
diff --git a/test/belongsToPolymorphic.test.js b/test/belongsToPolymorphic.test.js
index 7ab9c39..ff30961 100644
--- a/test/belongsToPolymorphic.test.js
+++ b/test/belongsToPolymorphic.test.js
@@ -106,4 +106,101 @@ describe('loopback json api belongsTo polymorphic relationships', function () {
       }
     )
   })
+
+  describe('File with no relationship to a Post', function () {
+    beforeEach(function (done) {
+      FileModel.create(
+        {
+          fileName: 'blah.jpg'
+        },
+        done
+      )
+    })
+
+    it('should return a null value for relationship data', function (done) {
+      request(app).get('/fileModels/1').end(function (err, res) {
+        expect(err).to.equal(null)
+        expect(res.body).to.not.have.key('errors')
+        expect(res.body.data.relationships.parent).to.be.an('object')
+        expect(res.body.data.relationships.parent.data).to.equal(null)
+        done()
+      })
+    })
+  })
+
+  describe('Create relationship via API', function () {
+    beforeEach(function (done) {
+      Post.create(
+        {
+          title: 'Post One',
+          content: 'Content'
+        },
+        done
+      )
+    })
+
+    it('should define a relationship to Post when file is created', function (
+      done
+    ) {
+      request(app)
+        .post('/fileModels')
+        .send({
+          data: {
+            type: 'fileModels',
+            attributes: {
+              fileName: 'blah.jpg'
+            },
+            relationships: {
+              parent: {
+                data: {
+                  id: 1,
+                  type: 'posts'
+                }
+              }
+            }
+          }
+        })
+        .set('accept', 'application/vnd.api+json')
+        .set('content-type', 'application/json')
+        .expect(201)
+        .end(function (err, res) {
+          expect(err).to.equal(null)
+          expect(res.body).to.not.have.key('errors')
+          expect(res.body.data.relationships.parent).to.be.an('object')
+          expect(res.body.data.relationships.parent.data).to.be.an('object')
+          done()
+        })
+    })
+
+    it('should ignore relationships with an invalid type', function (done) {
+      request(app)
+        .post('/fileModels')
+        .send({
+          data: {
+            type: 'fileModels',
+            attributes: {
+              fileName: 'blah.jpg'
+            },
+            relationships: {
+              parent: {
+                data: {
+                  id: 1,
+                  type: 'invalidType'
+                }
+              }
+            }
+          }
+        })
+        .set('accept', 'application/vnd.api+json')
+        .set('content-type', 'application/json')
+        .expect(201)
+        .end(function (err, res) {
+          expect(err).to.equal(null)
+          expect(res.body).to.not.have.key('errors')
+          expect(res.body.data.relationships.parent).to.be.an('object')
+          expect(res.body.data.relationships.parent.data).to.equal(null)
+          done()
+        })
+    })
+  })
 })
diff --git a/test/hasManyPolymorphic.test.js b/test/hasManyPolymorphic.test.js
index 1264be0..056b1ad 100644
--- a/test/hasManyPolymorphic.test.js
+++ b/test/hasManyPolymorphic.test.js
@@ -104,4 +104,60 @@ describe('loopback json api hasMany polymorphic relationships', function () {
       }
     )
   })
+
+  describe('Create relationship via API', function () {
+    beforeEach(function (done) {
+      Resource.create(
+        {
+          fileName: 'blah.jpg'
+        },
+        done
+      )
+    })
+
+    it(
+      'should define a relationship to Resources when Post is created',
+      function (done) {
+        Resource.create(
+          {
+            fileName: 'blah.jpg'
+          },
+          function (err, resource) {
+            expect(err).to.equal(null)
+            request(app)
+              .post('/posts')
+              .send({
+                data: {
+                  type: 'posts',
+                  attributes: {
+                    fileName: 'blah.jpg'
+                  },
+                  relationships: {
+                    resources: {
+                      data: [
+                        {
+                          id: 1,
+                          type: 'resources'
+                        }
+                      ]
+                    }
+                  }
+                }
+              })
+              .set('accept', 'application/vnd.api+json')
+              .set('content-type', 'application/json')
+              .expect(201)
+              .end(function (err, res) {
+                expect(err).to.equal(null)
+                expect(res.body).to.not.have.key('errors')
+                expect(res.body.data.relationships.resources).to.be.an(
+                  'object'
+                )
+                done()
+              })
+          }
+        )
+      }
+    )
+  })
 })