diff --git a/lib/fog/aws/requests/rds/modify_db_instance.rb b/lib/fog/aws/requests/rds/modify_db_instance.rb
index <HASH>..<HASH> 100644
--- a/lib/fog/aws/requests/rds/modify_db_instance.rb
+++ b/lib/fog/aws/requests/rds/modify_db_instance.rb
@@ -24,6 +24,7 @@ module Fog
         # * MultiAZ <~Boolean> Specifies if the DB Instance is a Multi-AZ deployment
         # * PreferredBackupWindow <~String> The daily time range during which automated backups are created if automated backups are enabled
         # * PreferredMaintenanceWindow <~String> The weekly time range (in UTC) during which system maintenance can occur, which may result in an outage
+        # * VpcSecurityGroups <~Array> A list of VPC Security Group IDs to authorize on this DB instance
         # ==== Returns
         # * response<~Excon::Response>:
         #   * body<~Hash>:
@@ -33,6 +34,10 @@ module Fog
             options.merge!(Fog::AWS.indexed_param('DBSecurityGroups.member.%d', [*security_groups]))
           end
 
+          if vpc_security_groups = options.delete('VpcSecurityGroups')
+            options.merge!(Fog::AWS.indexed_param('VpcSecurityGroupIds.member.%d', [*vpc_security_groups]))
+          end
+
           request({
             'Action'  => 'ModifyDBInstance',
             'DBInstanceIdentifier' => db_name,
Support VPC security group modifictions for RDS