diff --git a/gc.c b/gc.c
index 3be18818..910b425c 100644
--- a/gc.c
+++ b/gc.c
@@ -1483,6 +1483,17 @@ void gc_collector_sweep()
 
   CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
 
+// DEBUG diagnostics
+#if GC_DEBUG_SHOW_SWEEP_DIAG
+    for (heap_type = 0; heap_type < NUM_HEAP_TYPES; heap_type++) {
+      h = m->heap->heap[heap_type];
+      if (h) {
+        fprintf(stderr, "From collector - Heap %d diagnostics:\n", heap_type);
+        gc_print_stats(h);
+      }
+    }
+#endif
+
 // TODO: what to update in each heap? probably want to reset back to first heap in each mutator
 // may also need to set other things, clear color?