diff --git a/lib/graphiti/util/serializer_attributes.rb b/lib/graphiti/util/serializer_attributes.rb
index 7e895815..8994f529 100644
--- a/lib/graphiti/util/serializer_attributes.rb
+++ b/lib/graphiti/util/serializer_attributes.rb
@@ -13,7 +13,7 @@ def apply
         return unless readable?
 
         if @name == :id
-          @serializer.id(&@attr[:proc]) if @attr[:proc]
+          @serializer.id(&proc)
         elsif @attr[:proc]
           @serializer.send(_method, @name, serializer_options, &proc)
         else
diff --git a/spec/serialization_spec.rb b/spec/serialization_spec.rb
index 6f3c5410..d1f1a3cc 100644
--- a/spec/serialization_spec.rb
+++ b/spec/serialization_spec.rb
@@ -45,6 +45,33 @@ def self.name
       expect(json['data'][0]['attributes']).to eq('first_name' => 'John')
     end
 
+    context 'when id is custom type' do
+      before do
+        type = Dry::Types::Definition.new(String).constructor do |input|
+          'custom!'
+        end
+        Graphiti::Types[:custom] = {
+          params: type,
+          canonical_name: :string,
+          read: type,
+          write: type,
+          kind: 'scalar',
+          description: 'test'
+        }
+        resource.attribute :id, :custom
+      end
+
+      after do
+        Graphiti::Types.map.delete(:custom)
+      end
+
+      it 'goes through type coercion' do
+        PORO::Employee.create
+        render
+        expect(json['data'][0]['id']).to eq('custom!')
+      end
+    end
+
     describe 'helper functions' do
       let(:app_serializer) do
         Class.new(Graphiti::Serializer) do