diff --git a/src/netlist.c b/src/netlist.c
index 62757b94..6df779c7 100644
--- a/src/netlist.c
+++ b/src/netlist.c
@@ -1619,12 +1619,14 @@ void auto_set_wire_bus(int start, int end)
   if(xctx->netlist_count) return; /* do this only in top level */
   if(end > xctx->wires) return;
   if(start < 0) return;
+  if(!xctx->prep_hi_structs) return;
   cc = WIRELAYER; if(xctx->only_probes) cc = GRIDLAYER;
   regcomp(&re, "(.+\\[.+(:|\\.\\.)[^.]+\\])|(,)", REG_NOSUB | REG_EXTENDED);
 
   for(i = start;i < end; ++i) {
     bus = 0;
     oldbus = xctx->wire[i].bus;
+    if(!xctx->wire[i].node) continue;
     if(!regexec(&re, xctx->wire[i].node, 0 , NULL, 0) ) bus = 1;
     if( (oldbus == 0.0 && bus == 1) || (oldbus == -1.0 && bus == 0) ) {
       dbg(1, "auto_set_wire_bus(): i=%d, oldbus=%g bus=%d\n", i, oldbus, bus);