diff --git a/gc.c b/gc.c
index 84006494..38dcde1a 100644
--- a/gc.c
+++ b/gc.c
@@ -858,8 +858,10 @@ void gc_mut_cooperate(gc_thread_data *thd)
     }
     else if (thd->gc_status == STATUS_SYNC2) {
       // Mark thread "roots"
+printf("gc_cont %p\n", thd->gc_cont);
       gc_mark_gray(thd, thd->gc_cont);
       for (i = 0; i < thd->gc_num_args; i++) {
+printf("gc_args[%d] %p\n", i, thd->gc_args[i]);
         gc_mark_gray(thd, thd->gc_args[i]);
       }
       thd->gc_alloc_color = ATOMIC_GET(&gc_color_mark);
@@ -1016,7 +1018,7 @@ void gc_collector_mark_gray(object parent, object obj)
   // could lead to stack corruption.
   if (is_object_type(obj) && mark(obj) == gc_color_clear) {
     mark_stack = vpbuffer_add(mark_stack, &mark_stack_len, mark_stack_i++, obj);
-printf("mark gray parent = %p obj = %p\n", parent, obj);
+printf("mark gray parent = %p (%ld) obj = %p\n", parent, type_of(parent), obj);
   }
 }
 
diff --git a/runtime.c b/runtime.c
index da652d1e..9114ec66 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2441,6 +2441,7 @@ void gc_mark_globals()
   printf("(gc_mark_globals heap: %p size: %d)\n", h, (unsigned int)gc_heap_total_size(h));
 #endif
   // Mark global variables
+printf("Cyc_global_variables %p\n");
   gc_mark_black(Cyc_global_variables); // Internal global used by the runtime
                                        // Marking it ensures all glos are marked
   {
@@ -2449,6 +2450,7 @@ void gc_mark_globals()
      cvar_type *c = (cvar_type *)car(l);
      object glo =  *(c->pvar);
      if (!nullp(glo)) {
+printf("global pvar %p\n", glo);
        gc_mark_black(glo); // Mark actual object the global points to
      }
     }