diff --git a/init.rb b/init.rb
index 393775a6..ad53563d 100644
--- a/init.rb
+++ b/init.rb
@@ -220,9 +220,9 @@ Redmine::Plugin.register :redmine_dmsf do
         raise 'Not supported image format' unless file.image?
         url = url_for(:controller => :dmsf_files, :action => 'view', :id => file)      
         file_view_url = url_for(:controller => :dmsf_files, :action => 'view', :id => file, :download => args[2])
-        if size and size.include? "%"
+        if size && size.include?("%")
           img = image_tag(url, :alt => file.title, :width => size, :height => size)
-        elsif size and size.include? "x"
+        elsif size && size.include?("x")
           img = image_tag(url, :alt => file.title, :size => size)
         elsif height
           img = image_tag(url, :alt => file.title, :width => 'auto', :height => height)