diff --git a/plugins/category_generator.rb b/plugins/category_generator.rb
index 9beef9b..769a55b 100644
--- a/plugins/category_generator.rb
+++ b/plugins/category_generator.rb
@@ -174,8 +174,8 @@ ERR
# Returns string
def date_to_html_string(date)
result = '' + date.strftime('%b').upcase + ' '
- result += date.strftime('%d ')
- result += date.strftime('%Y ')
+ result << date.strftime('%d ')
+ result << date.strftime('%Y ')
result
end