diff --git a/lib/JSONAPISerializer.js b/lib/JSONAPISerializer.js
index 869c45f..67f2a62 100644
--- a/lib/JSONAPISerializer.js
+++ b/lib/JSONAPISerializer.js
@@ -435,7 +435,7 @@ module.exports = class JSONAPISerializer {
                   ? this.deserializeIncluded(
                       d.type,
                       d.id,
-                      options.relationships[relationshipProperty],
+                      options.relationships[relationshipKey],
                       included
                     )
                   : deserializeFunction(d)
@@ -452,7 +452,7 @@ module.exports = class JSONAPISerializer {
                 ? this.deserializeIncluded(
                     relationship.data.type,
                     relationship.data.id,
-                    options.relationships[relationshipProperty],
+                    options.relationships[relationshipKey],
                     included
                   )
                 : deserializeFunction(relationship.data)
diff --git a/test/unit/JSONAPISerializer.test.js b/test/unit/JSONAPISerializer.test.js
index 19ac2e6..adfb783 100644
--- a/test/unit/JSONAPISerializer.test.js
+++ b/test/unit/JSONAPISerializer.test.js
@@ -1533,7 +1533,15 @@ describe('JSONAPISerializer', function() {
 
     it('should deserialize with \'unconvertCase\' options', function(done) {
       const Serializer = new JSONAPISerializer();
-      Serializer.register('articles', {
+      Serializer.register('article', {
+        unconvertCase: 'snake_case',
+        relationships: {
+          article_author: {
+            type: 'people',
+          },
+        }
+      });
+      Serializer.register('people', {
         unconvertCase: 'snake_case',
       });
 
@@ -1552,23 +1560,28 @@ describe('JSONAPISerializer', function() {
               }
             }
           }
-        }
+        },
+        included: [{
+          type: 'people',
+          id: '1',
+          attributes: { firstName: 'Karl' }
+        }]
       };
 
-      const deserializedData = Serializer.deserialize('articles', data);
+      const deserializedData = Serializer.deserialize('article', data);
       expect(deserializedData).to.have.property('created_at');
-      expect(deserializedData).to.have.property('article_author');
+      expect(deserializedData.article_author).to.deep.equal({ id: '1', first_name: 'Karl' });
       done();
     });
 
     it('should deserialize with \'unconvertCase\' and \'deserialize\' options', function(done) {
       const Serializer = new JSONAPISerializer();
-      Serializer.register('articles', {
+      Serializer.register('article', {
         unconvertCase: 'snake_case',
         relationships: {
           article_author: {
-            deserialize: data => data.attributes,
-            type: 'authors',
+            deserialize: data => ({ id: data.id, additionalProperty: `${data.type}-${data.id}` }),
+            type: 'people',
           },
         }
       });
@@ -1584,16 +1597,16 @@ describe('JSONAPISerializer', function() {
             articleAuthor: {
               data: {
                 type: 'people',
-                attributes: { firstName: 'Karl' }
+                id: '1'
               }
             }
           }
         }
       };
 
-      const deserializedData = Serializer.deserialize('articles', data);
+      const deserializedData = Serializer.deserialize('article', data);
       expect(deserializedData).to.have.property('created_at');
-      expect(deserializedData.article_author).to.deep.equal({ first_name: 'Karl' });
+      expect(deserializedData.article_author).to.deep.equal({ id: '1', additional_property: 'people-1' });
       done();
     });