diff --git a/lib/active_record/connection_adapters/mysql2_adapter.rb b/lib/active_record/connection_adapters/mysql2_adapter.rb
index 825dd44..b5b5e83 100644
--- a/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -241,7 +241,10 @@ module ActiveRecord
       end
 
       def disconnect!
-        @connection.close
+        unless @connection.nil?
+          @connection.close
+          @connection = nil
+        end
       end
 
       def reset!