Replacing old block with new one.

lib/annotate/annotate_models.rb

@@ -241,6 +241,9 @@ module AnnotateModels
 #           end
 # =======
 
+          if PATTERN.match(old_content)
+            new_content = old_content.sub(PATTERN, info_block)
+          else
             # Strip the old schema info, and insert new schema info.
             old_content.sub!(encoding, '')
             old_content.sub!(PATTERN, '')
@@ -248,6 +251,7 @@ module AnnotateModels
             new_content = options[position].to_s == 'after' ?
               (encoding_header + (old_content.rstrip + "\n\n" + info_block)) :
               (encoding_header + info_block + "\n" + old_content)
+          end
 
           File.open(file_name, "wb") { |f| f.puts new_content }
           return true