diff --git a/lib/fog/aws/requests/rds/create_db_subnet_group.rb b/lib/fog/aws/requests/rds/create_db_subnet_group.rb
index 0c4d37c1f..46c189cc5 100644
--- a/lib/fog/aws/requests/rds/create_db_subnet_group.rb
+++ b/lib/fog/aws/requests/rds/create_db_subnet_group.rb
@@ -31,15 +31,14 @@ module Fog
           end
 
           # collection = Fog::Compute::AWS.new(:aws_access_key_id => 'mock key', :aws_secret_access_key => 'mock secret')
-          collection = Fog::Compute[:aws]
-          collection.region = @region
+          compute_data = Fog::Compute::AWS::Mock.data[self.region][self.aws_access_key_id]
 
           subnets = subnet_ids.map do |snid|
-            subnet = collection.subnets.get(snid)
+            subnet = compute_data[:subnets].detect { |s| s['subnetId'] == snid }
             raise Fog::AWS::RDS::NotFound.new("InvalidSubnet => The subnet '#{snid}' was not found") if subnet.nil?
             subnet
           end
-          vpc_id = subnets.first.vpc_id
+          vpc_id = subnets.first['vpcId']
 
           data = {
             'DBSubnetGroupName' => name,