diff --git a/main.tf b/main.tf
index a645c86..05a26fd 100644
--- a/main.tf
+++ b/main.tf
@@ -41,7 +41,7 @@ resource "openstack_networking_secgroup_rule_v2" "egress" {
 
   description      = try(each.value.description, false) != false ? each.value.description : "Terraform managed."
   ethertype        = try(each.value.ethertype, false) != false ? each.value.ethertype : "IPv4"
-  protocol         = try(each.value.protocol, false) != false ? each.value.protocol : "tcp"
+  protocol         = try(each.value.protocol, false) != false ? each.value.protocol : null
   port_range_min   = try(each.value.port_range_min, false) != false ? each.value.port_range_min : null
   port_range_max   = try(each.value.port_range_max, false) != false ? each.value.port_range_max : null
   remote_ip_prefix = try(each.value.remote_ip_prefix, false) != false ? each.value.remote_ip_prefix : null