diff --git a/terraform/environments/delius-core/modules/components/oracle_db_shared/sg.tf b/terraform/environments/delius-core/modules/components/oracle_db_shared/sg.tf
index 6b68557ea03..65db3983279 100644
--- a/terraform/environments/delius-core/modules/components/oracle_db_shared/sg.tf
+++ b/terraform/environments/delius-core/modules/components/oracle_db_shared/sg.tf
@@ -52,6 +52,15 @@ resource "aws_vpc_security_group_egress_rule" "db_inter_conn" {
   referenced_security_group_id = aws_security_group.db_ec2.id
 }
 
+resource "aws_vpc_security_group_ingress_rule" "db_inter_conn" {
+  security_group_id            = aws_security_group.db_ec2.id
+  description                  = "Allow communication between delius db instances"
+  from_port                    = 1521
+  to_port                      = 1521
+  ip_protocol                  = "tcp"
+  referenced_security_group_id = aws_security_group.db_ec2.id
+}
+
 resource "aws_vpc_security_group_ingress_rule" "delius_db_security_group_ingress_bastion" {
   security_group_id            = aws_security_group.db_ec2.id
   description                  = "bastion to testing db"