diff --git a/.gitignore b/.gitignore
index 7e2daa8f..e4c844d6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 /redmine_dmsf.iml
 Gemfile.lock
 .history
+tmp/
diff --git a/app/helpers/dmsf_links_helper.rb b/app/helpers/dmsf_links_helper.rb
index 026d04e5..2cef3da6 100644
--- a/app/helpers/dmsf_links_helper.rb
+++ b/app/helpers/dmsf_links_helper.rb
@@ -35,7 +35,7 @@ module DmsfLinksHelper
     str&.match?(/\A\d+\Z/)
   end
 
-  def files_for_select(project_id, folder_id)
+  def files_for_select(project_id, folder_id = nil)
     files = []
     if DmsfLinksHelper.number?(folder_id)
       folder = DmsfFolder.find_by(id: folder_id)
diff --git a/app/views/dmsf_links/_form.html.erb b/app/views/dmsf_links/_form.html.erb
index df1bc658..7a31cd11 100644
--- a/app/views/dmsf_links/_form.html.erb
+++ b/app/views/dmsf_links/_form.html.erb
@@ -110,8 +110,8 @@
     </div>
   </div>
 <% end %>
-
 <%= late_javascript_tag do %>
+$(document).ready(function(){
   <%# Select2 extension, TODO: in case of a modal window, select2 makes problems %>
   <% unless modal || @fast_links %>
     $('#dmsf_link_target_project_id').select2();
@@ -148,4 +148,5 @@
       labelUrl.append('<span class="required"> *</span>');
     }
   });
+});
 <% end %>
diff --git a/test/helpers/dmsf_links_helper_test.rb b/test/helpers/dmsf_links_helper_test.rb
index 60066470..15228294 100644
--- a/test/helpers/dmsf_links_helper_test.rb
+++ b/test/helpers/dmsf_links_helper_test.rb
@@ -31,4 +31,11 @@ class DmsfLinksHelperTest < RedmineDmsf::Test::HelperTest
     assert_not DmsfLinksHelper.number?('123a')
     assert_not DmsfLinksHelper.number?(nil)
   end
+
+  def test_default_folder_id_in_files_for_select
+    project = Project.find(1)
+    assert_nothing_raised do
+      files_for_select(project.id)
+    end
+  end
 end