diff --git a/lib/fast_jsonapi/object_serializer.rb b/lib/fast_jsonapi/object_serializer.rb
index afa6bb2..fa13add 100644
--- a/lib/fast_jsonapi/object_serializer.rb
+++ b/lib/fast_jsonapi/object_serializer.rb
@@ -130,6 +130,7 @@ module FastJsonapi
         subclass.cached = cached
         subclass.set_type(subclass.reflected_record_type) if subclass.reflected_record_type
         subclass.meta_to_serialize = meta_to_serialize
+        subclass.record_id = record_id
       end
 
       def reflected_record_type
@@ -241,12 +242,15 @@ module FastJsonapi
           base_key_sym = name
           id_postfix = '_id'
         end
+        polymorphic = fetch_polymorphic_option(options)
+
         Relationship.new(
           key: options[:key] || run_key_transform(base_key),
           name: name,
           id_method_name: compute_id_method_name(
             options[:id_method_name],
             "#{base_serialization_key}#{id_postfix}".to_sym,
+            polymorphic,
             block
           ),
           record_type: options[:record_type] || run_key_transform(base_key_sym),
@@ -255,7 +259,7 @@ module FastJsonapi
           serializer: compute_serializer_name(options[:serializer] || base_key_sym),
           relationship_type: relationship_type,
           cached: options[:cached],
-          polymorphic: fetch_polymorphic_option(options),
+          polymorphic: polymorphic,
           conditional_proc: options[:if],
           transform_method: @transform_method,
           links: options[:links],
@@ -263,8 +267,8 @@ module FastJsonapi
         )
       end
 
-      def compute_id_method_name(custom_id_method_name, id_method_name_from_relationship, block)
-        if block.present?
+      def compute_id_method_name(custom_id_method_name, id_method_name_from_relationship, polymorphic, block)
+        if block.present? || polymorphic
           custom_id_method_name || :id
         else
           custom_id_method_name || id_method_name_from_relationship
diff --git a/lib/fast_jsonapi/relationship.rb b/lib/fast_jsonapi/relationship.rb
index 5f82843..12b5a1a 100644
--- a/lib/fast_jsonapi/relationship.rb
+++ b/lib/fast_jsonapi/relationship.rb
@@ -78,7 +78,7 @@ module FastJsonapi
     def id_hash_from_record(record, record_types)
       # memoize the record type within the record_types dictionary, then assigning to record_type:
       associated_record_type = record_types[record.class] ||= run_key_transform(record.class.name.demodulize.underscore)
-      id_hash(record.id, associated_record_type)
+      id_hash(record.public_send(id_method_name), associated_record_type)
     end
 
     def ids_hash(ids)
diff --git a/spec/lib/object_serializer_inheritance_spec.rb b/spec/lib/object_serializer_inheritance_spec.rb
index beb7487..8e1b0d7 100644
--- a/spec/lib/object_serializer_inheritance_spec.rb
+++ b/spec/lib/object_serializer_inheritance_spec.rb
@@ -20,7 +20,7 @@ describe FastJsonapi::ObjectSerializer do
   end
 
   class User
-    attr_accessor :id, :first_name, :last_name
+    attr_accessor :id, :first_name, :last_name, :uuid
 
     attr_accessor :address_ids, :country_id
 
@@ -39,6 +39,7 @@ describe FastJsonapi::ObjectSerializer do
   class UserSerializer
     include FastJsonapi::ObjectSerializer
     set_type :user
+    set_id :uuid
     attributes :first_name, :last_name
 
     attribute :full_name do |user, params|
@@ -125,6 +126,14 @@ describe FastJsonapi::ObjectSerializer do
       EmployeeSerializer
       expect(UserSerializer.attributes_to_serialize).not_to have_key(:location)
     end
+
+    it 'inherits the id source' do
+      e = Employee.new
+      e.id = 2
+      e.uuid = SecureRandom.uuid
+      id = EmployeeSerializer.new(e).serializable_hash[:data][:id]
+      expect(id).to eq(e.uuid)
+    end
   end
 
   context 'when testing inheritance of relationship' do
@@ -158,11 +167,9 @@ describe FastJsonapi::ObjectSerializer do
   end
 
   context 'when test inheritence of other attributes' do
-
     it 'inherits the tranform method' do
       EmployeeSerializer
       expect(UserSerializer.transform_method).to eq EmployeeSerializer.transform_method
     end
-
   end
 end
diff --git a/spec/lib/object_serializer_polymorphic_spec.rb b/spec/lib/object_serializer_polymorphic_spec.rb
index f889141..253fbef 100644
--- a/spec/lib/object_serializer_polymorphic_spec.rb
+++ b/spec/lib/object_serializer_polymorphic_spec.rb
@@ -13,6 +13,10 @@ describe FastJsonapi::ObjectSerializer do
     attr_accessor :id, :model, :year
   end
 
+  class Animal
+    attr_accessor :id, :uuid, :species
+  end
+
   class ListSerializer
     include FastJsonapi::ObjectSerializer
     set_type :list
@@ -21,6 +25,13 @@ describe FastJsonapi::ObjectSerializer do
     has_many :items, polymorphic: true
   end
 
+  class ZooSerializer
+    include FastJsonapi::ObjectSerializer
+    set_type :list
+    attributes :name
+    has_many :items, polymorphic: true, id_method_name: :uuid
+  end
+
   let(:car) do
     car = Car.new
     car.id = 1
@@ -36,6 +47,14 @@ describe FastJsonapi::ObjectSerializer do
     checklist_item
   end
 
+  let(:animal) do
+    animal = Animal.new
+    animal.id = 1
+    animal.species = 'Mellivora capensis'
+    animal.uuid = SecureRandom.uuid
+    animal
+  end
+
   context 'when serializing id and type of polymorphic relationships' do
     it 'should return correct type when transform_method is specified' do
       list = List.new
@@ -47,5 +66,14 @@ describe FastJsonapi::ObjectSerializer do
       record_type = list_hash[:data][:relationships][:items][:data][1][:type]
       expect(record_type).to eq 'car'.to_sym
     end
+
+    it 'should use the correct id method on associated objects' do
+      list = List.new
+      list.id = 1
+      list.items = [animal]
+      list_hash = ZooSerializer.new(list).to_hash
+      id = list_hash[:data][:relationships][:items][:data][0][:id]
+      expect(id).to eq animal.uuid
+    end
   end
 end