diff --git a/moto/ec2/responses/nat_gateways.py b/moto/ec2/responses/nat_gateways.py
index e960b990..98d383d4 100644
--- a/moto/ec2/responses/nat_gateways.py
+++ b/moto/ec2/responses/nat_gateways.py
@@ -6,14 +6,14 @@ from moto.ec2.utils import filters_from_querystring
 class NatGateways(BaseResponse):
 
     def create_nat_gateway(self):
-        subnet_id = self.querystring.get('SubnetId')[0]
-        allocation_id = self.querystring.get('AllocationId')[0]
+        subnet_id = self._get_param('SubnetId')
+        allocation_id = self._get_param('AllocationId')
         nat_gateway = self.ec2_backend.create_nat_gateway(subnet_id=subnet_id, allocation_id=allocation_id)
         template = self.response_template(CREATE_NAT_GATEWAY)
         return template.render(nat_gateway=nat_gateway)
 
     def delete_nat_gateway(self):
-        nat_gateway_id = self.querystring.get('NatGatewayId')[0]
+        nat_gateway_id = self._get_param('NatGatewayId')
         nat_gateway = self.ec2_backend.delete_nat_gateway(nat_gateway_id)
         template = self.response_template(DELETE_NAT_GATEWAY_RESPONSE)
         return template.render(nat_gateway=nat_gateway)