1 files changed, 4 insertions, 4 deletions
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index e372b3a816..812565b207 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -119,12 +119,11 @@ defaults to `:debug` for all environments. The available log levels are: `:debug
 * `config.logger` is the logger that will be used for `Rails.logger` and any related Rails logging such as `ActiveRecord::Base.logger`. It defaults to an instance of `ActiveSupport::TaggedLogging` that wraps an instance of `ActiveSupport::Logger` which outputs a log to the `log/` directory. You can supply a custom logger, to get full compatibility you must follow these guidelines:
   * To support a formatter, you must manually assign a formatter from the `config.log_formatter` value to the logger.
   * To support tagged logs, the log instance must be wrapped with `ActiveSupport::TaggedLogging`.
-  * To support silencing, the logger must include `LoggerSilence` and `ActiveSupport::LoggerThreadSafeLevel` modules. The `ActiveSupport::Logger` class already includes these modules.
+  * To support silencing, the logger must include `ActiveSupport::LoggerSilence`  module. The `ActiveSupport::Logger` class already includes these modules.
 
     ```ruby
     class MyLogger < ::Logger
-      include ActiveSupport::LoggerThreadSafeLevel
-      include LoggerSilence
+      include ActiveSupport::LoggerSilence
     end
 
     mylogger           = MyLogger.new(STDOUT)
@@ -1014,7 +1013,6 @@ If you choose to use MySQL or MariaDB instead of the shipped SQLite3 database, y
 ```yaml
 development:
   adapter: mysql2
-  encoding: utf8
   database: blog_development
   pool: 5
   username: root
@@ -1024,6 +1022,8 @@ development:
 
 If your development database has a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the `development` section as appropriate.
 
+NOTE: If your MySQL version is 5.5 or 5.6 and want to use the `utf8mb4` character set by default, please configure your MySQL server to support the longer key prefix by enabling `innodb_large_prefix` system variable.
+
 Advisory Locks are enabled by default on MySQL and are used to make database migrations concurrent safe. You can disable advisory locks by setting `advisory_locks` to `false`:
 
 ```yaml