diff --git a/src/vnet/mpls/mpls_api.c b/src/vnet/mpls/mpls_api.c
index 4efb617..fac5282 100644
--- a/src/vnet/mpls/mpls_api.c
+++ b/src/vnet/mpls/mpls_api.c
@@ -508,7 +508,8 @@
   /*
    * Trace space for 8 MPLS encap labels
    */
-  am->api_trace_cfg[VL_API_MPLS_TUNNEL_ADD_DEL].size += 8 * sizeof (u32);
+  vl_api_increase_msg_trace_size (am, VL_API_MPLS_TUNNEL_ADD_DEL,
+				  8 * sizeof (u32));
 
   /*
    * Set up the (msg_name, crc, message-id) table