diff --git a/libguile/whippet-embedder.h b/libguile/whippet-embedder.h
index e09f017f5..46fafefa6 100644
--- a/libguile/whippet-embedder.h
+++ b/libguile/whippet-embedder.h
@@ -199,7 +199,7 @@ gc_atomic_forward_retry_busy (struct gc_atomic_forward *fwd) {
   scm_t_bits tag = atomic_load_explicit (loc, memory_order_acquire);
   if (tag == scm_cell_type_busy)
     return 0;
-  if ((tag & 7) == scm_tc3_forwarded) {
+  if ((tag & scm_tc3_mask) == scm_tc3_forwarded) {
     fwd->state = GC_FORWARDING_STATE_FORWARDED;
     fwd->data = tag;
   } else {