diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index 6bf7af081f28d8fada3595dafb188290e06c57aa..bb63fddf9b8772c413b3a166fea476d9a3c4ca6b 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -7,8 +7,6 @@
 
 class Mysql
   class Time
-    ###
-    # This monkey patch is for test_additional_columns_from_join_table
     def to_date
       Date.new(year, month, day)
     end
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index 4c6d4666edfeff2f957ff0fd0b03c96a2d90a766..f39111ba77abbe8ffeb5c34a21d192c2c26b55df 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -22,6 +22,8 @@
 # Connect to the database
 ARTest.connect
 
+require 'support/mysql'
+
 # Quote "type" if it's a reserved word for the current connection.
 QUOTED_TYPE = ActiveRecord::Base.connection.quote_column_name('type')
 
diff --git a/activerecord/test/support/mysql.rb b/activerecord/test/support/mysql.rb
new file mode 100644
index 0000000000000000000000000000000000000000..7a66415e64a836a5f0ca78a55b4b03846a4183d7
--- /dev/null
+++ b/activerecord/test/support/mysql.rb
@@ -0,0 +1,11 @@
+if defined?(Mysql)
+  class Mysql
+    class Error
+      # This monkey patch fixes annoy warning with mysql-2.8.1.gem when executing testcases.
+      def errno_with_fix_warnings
+        silence_warnings { errno_without_fix_warnings }
+      end
+      alias_method_chain :errno, :fix_warnings
+    end
+  end
+end