diff --git a/tb_pulumi/rds.py b/tb_pulumi/rds.py
index 0f01d88..c30f4cb 100644
--- a/tb_pulumi/rds.py
+++ b/tb_pulumi/rds.py
@@ -412,7 +412,7 @@ def __init__(
         port = SERVICE_PORTS.get(engine, 5432)
         inst_addrs = [instance.address for instance in instances]
         load_balancer_ips = pulumi.Output.all(*inst_addrs).apply(
-            lambda addresses: [socket.gethostbyname(addr) for addr in addresses]
+            lambda addresses: ','.join([socket.gethostbyname(addr) for addr in addresses])
         )
         pulumi.info(f'LOAD BALANCER IPS: {load_balancer_ips}')
         load_balancer = tb_pulumi.ec2.NetworkLoadBalancer(
@@ -424,7 +424,7 @@ def __init__(
             target_port=port,
             ingress_cidrs=[vpc_cidr],
             internal=True,
-            ips=load_balancer_ips,
+            ips=load_balancer_ips.split(','),
             security_group_description=f'Allow database traffic for {name}',
             opts=pulumi.ResourceOptions(parent=self, depends_on=[*instances, load_balancer_ips, *subnets]),
         )