diff --git a/src/vnet/session/session.api b/src/vnet/session/session.api
index b897ae0..2f5e452 100644
--- a/src/vnet/session/session.api
+++ b/src/vnet/session/session.api
@@ -218,7 +218,7 @@
   u32 client_index;
   u32 context;
   u64 secret;
-  vl_api_interface_index_t sw_if_index;
+  vl_api_interface_index_t sw_if_index [default=0xffffffff];
   u32 ip4_fib_id;
   u32 ip6_fib_id;
   string namespace_id[];