diff --git a/app/services/proforma_service/convert_task_to_exercise.rb b/app/services/proforma_service/convert_task_to_exercise.rb
index 222a56b8..f9682bf3 100644
--- a/app/services/proforma_service/convert_task_to_exercise.rb
+++ b/app/services/proforma_service/convert_task_to_exercise.rb
@@ -101,7 +101,7 @@ module ProformaService
     end
 
     def file_type(extension)
-      FileType.find_or_create_by(file_extension: extension) do |file_type|
+      FileType.find_or_create_by(file_extension: extension.presence) do |file_type|
         file_type.name = extension[1..]
         file_type.user = @user
         file_type.indent_size = 4
diff --git a/spec/services/proforma_service/convert_task_to_exercise_spec.rb b/spec/services/proforma_service/convert_task_to_exercise_spec.rb
index b5b685d7..38439c95 100644
--- a/spec/services/proforma_service/convert_task_to_exercise_spec.rb
+++ b/spec/services/proforma_service/convert_task_to_exercise_spec.rb
@@ -232,6 +232,20 @@ describe ProformaService::ConvertTaskToExercise do
           expect { convert_to_exercise_service.save! }.to change(FileType, :count).by(1)
         end
       end
+
+      context 'when file has a Makefile' do
+        let!(:file_type) { create(:makefile) }
+
+        let(:filename) { 'Makefile' }
+
+        it 'creates a new Exercise on save' do
+          expect { convert_to_exercise_service.save! }.to change(Exercise, :count).by(1)
+        end
+
+        it 'creates an exercise with a file with correct attributes' do
+          expect(convert_to_exercise_service.files.first.file_type).to eql file_type
+        end
+      end
     end
 
     context 'when task has a model-solution' do