diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 1e2f2703..75cae0a5 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -146,6 +146,8 @@ void gc_thread_data_free(gc_thread_data *thd);
 // Prototypes for mutator/collector:
 void gc_mut_update(gc_thread_data *thd, object old_obj, object value);
 void gc_mut_cooperate(gc_thread_data *thd);
+void gc_stack_mark_refs_gray(gc_thread_data *thd, object obj);
+void gc_stack_mark_gray(gc_thread_data *thd, object obj);
 void gc_mark_gray(gc_thread_data *thd, object obj);
 void gc_collector_trace();
 void gc_mark_black(object obj);
@@ -342,7 +344,7 @@ typedef cons_type *list;
 #define cddddr(x) (cdr(cdr(cdr(cdr(x)))))
 
 #define make_cons(n,a,d) \
-cons_type n; n.tag = cons_tag; n.cons_car = a; n.cons_cdr = d;
+cons_type n; n.hdr.mark = gc_color_red; n.tag = cons_tag; n.cons_car = a; n.cons_cdr = d;
 
 /* Closure types */