diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
index b043f9e98..4701b088f 100644
--- a/northd/ovn-northd.c
+++ b/northd/ovn-northd.c
@@ -4775,13 +4775,10 @@ build_lswitch_input_port_sec_od(
 }
 
 static void
-build_lswitch_output_port_sec(struct hmap *ports, struct hmap *datapaths,
-                              struct hmap *lflows)
+build_lswitch_output_port_sec_op(
+        struct ovn_port *op, struct hmap *lflows,
+        struct ds *match, struct ds *actions)
 {
-    struct ds actions = DS_EMPTY_INITIALIZER;
-    struct ds match = DS_EMPTY_INITIALIZER;
-    struct ovn_port *op;
-
     /* Egress table 8: Egress port security - IP (priorities 90 and 80)
      * if port security enabled.
      *
@@ -4792,57 +4789,53 @@ build_lswitch_output_port_sec(struct hmap *ports, struct hmap *datapaths,
      * Priority 150 rules drop packets to disabled logical ports, so that
      * they don't even receive multicast or broadcast packets.
      */
-    HMAP_FOR_EACH (op, key_node, ports) {
-        if (!op->nbsp || lsp_is_external(op->nbsp)) {
-            continue;
-        }
+    if (!op->nbsp || lsp_is_external(op->nbsp)) {
+        return;
+    }
 
-        ds_clear(&actions);
-        ds_clear(&match);
+    ds_clear(actions);
+    ds_clear(match);
 
-        ds_put_format(&match, "outport == %s", op->json_key);
-        if (lsp_is_enabled(op->nbsp)) {
-            build_port_security_l2("eth.dst", op->ps_addrs, op->n_ps_addrs,
-                                   &match);
+    ds_put_format(match, "outport == %s", op->json_key);
+    if (lsp_is_enabled(op->nbsp)) {
+        build_port_security_l2("eth.dst", op->ps_addrs, op->n_ps_addrs,
+                               match);
 
-            if (!strcmp(op->nbsp->type, "localnet")) {
-                const char *queue_id = smap_get(&op->sb->options,
-                                                "qdisc_queue_id");
-                if (queue_id) {
-                    ds_put_format(&actions, "set_queue(%s); ", queue_id);
-                }
+        if (!strcmp(op->nbsp->type, "localnet")) {
+            const char *queue_id = smap_get(&op->sb->options,
+                                            "qdisc_queue_id");
+            if (queue_id) {
+                ds_put_format(actions, "set_queue(%s); ", queue_id);
             }
-            ds_put_cstr(&actions, "output;");
-            ovn_lflow_add_with_hint(lflows, op->od, S_SWITCH_OUT_PORT_SEC_L2,
-                                    50, ds_cstr(&match), ds_cstr(&actions),
-                                    &op->nbsp->header_);
-        } else {
-            ovn_lflow_add_with_hint(lflows, op->od, S_SWITCH_OUT_PORT_SEC_L2,
-                                    150, ds_cstr(&match), "drop;",
-                                    &op->nbsp->header_);
         }
+        ds_put_cstr(actions, "output;");
+        ovn_lflow_add_with_hint(lflows, op->od, S_SWITCH_OUT_PORT_SEC_L2,
+                                50, ds_cstr(match), ds_cstr(actions),
+                                &op->nbsp->header_);
+    } else {
+        ovn_lflow_add_with_hint(lflows, op->od, S_SWITCH_OUT_PORT_SEC_L2,
+                                150, ds_cstr(match), "drop;",
+                                &op->nbsp->header_);
+    }
 
-        if (op->nbsp->n_port_security) {
-            build_port_security_ip(P_OUT, op, lflows, &op->nbsp->header_);
-        }
+    if (op->nbsp->n_port_security) {
+        build_port_security_ip(P_OUT, op, lflows, &op->nbsp->header_);
     }
+}
+
+static void
+build_lswitch_output_port_sec_od(
+        struct ovn_datapath *od, struct hmap *lflows)
+{
 
     /* Egress tables 8: Egress port security - IP (priority 0)
      * Egress table 9: Egress port security L2 - multicast/broadcast
      *                 (priority 100). */
-    struct ovn_datapath *od;
-    HMAP_FOR_EACH (od, key_node, datapaths) {
-        if (!od->nbs) {
-            continue;
-        }
-
+    if (od->nbs) {
         ovn_lflow_add(lflows, od, S_SWITCH_OUT_PORT_SEC_IP, 0, "1", "next;");
         ovn_lflow_add(lflows, od, S_SWITCH_OUT_PORT_SEC_L2, 100, "eth.mcast",
                       "output;");
     }
-
-    ds_destroy(&match);
-    ds_destroy(&actions);
 }
 
 static void
@@ -6785,7 +6778,11 @@ build_lswitch_flows(struct hmap *datapaths, struct hmap *ports,
                 op, lflows, mcgroups, &match, &actions);
     }
 
-    /* Ingress table 19: Destination lookup for unknown MACs (priority 0). */
+    /* Ingress table 19: Destination lookup for unknown MACs (priority 0). 
+     * This cannot be parallelised because has_unknown is modified in 
+     * build_lswitch_destination_lookup_and_unicast_op() so leaving it 
+     * "as is" */
+
     HMAP_FOR_EACH (od, key_node, datapaths) {
         if (!od->nbs) {
             continue;
@@ -6797,7 +6794,14 @@ build_lswitch_flows(struct hmap *datapaths, struct hmap *ports,
         }
     }
 
-    build_lswitch_output_port_sec(ports, datapaths, lflows);
+    HMAP_FOR_EACH (op, key_node, ports) {
+        build_lswitch_output_port_sec_op(
+                op, lflows, &match, &actions);
+    }
+
+    HMAP_FOR_EACH (od, key_node, datapaths) {
+        build_lswitch_output_port_sec_od(od, lflows);
+    }
 
     ds_destroy(&match);
     ds_destroy(&actions);
