diff --git a/lib/rails-footnotes/abstract_note.rb b/lib/rails-footnotes/abstract_note.rb
index 01d8300..b98a7da 100644
--- a/lib/rails-footnotes/abstract_note.rb
+++ b/lib/rails-footnotes/abstract_note.rb
@@ -169,7 +169,7 @@ def mount_table_for_hash(hash, options={})
         def hash_to_xml_attributes(hash)
           newstring = ""
           hash.each do |key, value|
-            newstring << "#{key.to_s}=\"#{value.gsub('"','\"')}\" "
+            newstring += "#{key.to_s}=\"#{value.gsub('"','\"')}\" "
           end
           return newstring
         end
diff --git a/lib/rails-footnotes/filter.rb b/lib/rails-footnotes/filter.rb
index d9a69e6..935a482 100644
--- a/lib/rails-footnotes/filter.rb
+++ b/lib/rails-footnotes/filter.rb
@@ -287,7 +287,7 @@ def links
         html = ''
         order.uniq!
         order.each do |row|
-          html << "#{row.is_a?(String) ? row : row.to_s.camelize}: #{links[row].join(" | \n")}<br />"
+          html += "#{row.is_a?(String) ? row : row.to_s.camelize}: #{links[row].join(" | \n")}<br />"
         end
         html
       end
@@ -298,7 +298,7 @@ def fieldsets
         content = ''
         each_with_rescue(@notes) do |note|
           next unless note.has_fieldset?
-          content << <<-HTML
+          content += <<-HTML
             <fieldset id="#{note.to_sym}_debug_info" style="display: none">
               <legend>#{note.legend}</legend>
               <div>#{note.content}</div>
@@ -315,7 +315,7 @@ def close
         javascript = ''
         each_with_rescue(@notes) do |note|
           next unless note.has_fieldset?
-          javascript << close_helper(note)
+          javascript += close_helper(note)
         end
         javascript
       end
diff --git a/lib/rails-footnotes/notes/log_note.rb b/lib/rails-footnotes/notes/log_note.rb
index 92d27b6..0a1e02e 100644
--- a/lib/rails-footnotes/notes/log_note.rb
+++ b/lib/rails-footnotes/notes/log_note.rb
@@ -33,9 +33,9 @@ def title
       def content
         result = '<table>'
           log.compact.each do |l|
-            result << "<tr><td>#{l.gsub(/\e\[.+?m/, '')}</td></tr>"
+            result += "<tr><td>#{l.gsub(/\e\[.+?m/, '')}</td></tr>"
           end
-        result << '</table>'
+        result += '</table>'
         # Restore formatter
         Rails.logger = self.class.original_logger
         result
diff --git a/lib/rails-footnotes/notes/queries_note.rb b/lib/rails-footnotes/notes/queries_note.rb
index a637144..9074e61 100644
--- a/lib/rails-footnotes/notes/queries_note.rb
+++ b/lib/rails-footnotes/notes/queries_note.rb
@@ -36,7 +36,7 @@ def content
           sql_links = []
           sql_links << "<a href=\"javascript:Footnotes.toggle('qtrace_#{index}')\" style=\"color:#00A;\">trace</a>"
 
-          html << <<-HTML
+          html += <<-HTML
           <tr>
             <td>
               <b id="qtitle_#{index}">#{escape(event.type.to_s.upcase)}</b> (#{sql_links.join(' | ')})
@@ -49,7 +49,7 @@ def content
           </tr>
           HTML
         end
-        html << '</table>'
+        html += '</table>'
         return html
       end