diff --git a/src/vnet/ipip/ipip.c b/src/vnet/ipip/ipip.c
index fc71b5b..d68e815 100644
--- a/src/vnet/ipip/ipip.c
+++ b/src/vnet/ipip/ipip.c
@@ -430,7 +430,11 @@
   };
   t = ipip_tunnel_db_find (&key);
   if (t)
-    return VNET_API_ERROR_IF_ALREADY_EXISTS;
+    {
+      if (sw_if_indexp)
+	sw_if_indexp[0] = t->sw_if_index;
+      return VNET_API_ERROR_IF_ALREADY_EXISTS;
+    }
 
   pool_get_aligned (gm->tunnels, t, CLIB_CACHE_LINE_BYTES);
   clib_memset (t, 0, sizeof (*t));