diff --git a/nexus/arch.cc b/nexus/arch.cc
index 08a9a4c2..f804cdd9 100644
--- a/nexus/arch.cc
+++ b/nexus/arch.cc
@@ -632,7 +632,10 @@ bool Arch::place()
         cfg.ioBufTypes.insert(id_SEIO33_CORE);
         cfg.ioBufTypes.insert(id_SEIO18_CORE);
         cfg.ioBufTypes.insert(id_OSC_CORE);
-        cfg.placeAllAtOnce = true;
+        cfg.cellGroups.emplace_back();
+        cfg.cellGroups.back().insert({id_OXIDE_COMB});
+        cfg.cellGroups.back().insert({id_OXIDE_FF});
+
         cfg.beta = 0.5;
         cfg.criticalityExponent = 7;
         if (!placer_heap(getCtx(), cfg))