diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 0d5a8e6f25..fa2522c2d2 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -207,7 +207,7 @@ module ActiveRecord
     #
     # The keys of the hash which is the value for +:posts_attributes+ are
     # ignored in this case.
-    # However, it is not allowed to use +'id'+ or +:id+ for one of
+    # However, it is not allowed to use <tt>'id'</tt> or <tt>:id</tt> for one of
     # such keys, otherwise the hash will be wrapped in an array and
     # interpreted as an attribute hash for a single post.
     #