diff --git a/serv.core b/serv.core
index 88d6d95..de9b5a9 100644
--- a/serv.core
+++ b/serv.core
@@ -25,6 +25,7 @@ targets:
   default:
     filesets : [core]
     parameters : [RISCV_FORMAL, SERV_CLEAR_RAM]
+    toplevel : ["is_toplevel? (serv_top)"]
 
   lint:
     default_tool : verilator