diff --git a/src/boot/be/abi.ml b/src/boot/be/abi.ml
index fd9ca750e91..adad9d77a78 100644
--- a/src/boot/be/abi.ml
+++ b/src/boot/be/abi.ml
@@ -29,15 +29,16 @@ let frame_glue_fns_field_reloc = 2;;
 let exterior_rc_slot_field_refcnt = 0;;
 let exterior_rc_slot_field_body = 1;;
 
+let exterior_gc_slot_field_prev = (-3);;
 let exterior_gc_slot_field_next = (-2);;
 let exterior_gc_slot_field_ctrl = (-1);;
 let exterior_gc_slot_field_refcnt = 0;;
 let exterior_gc_slot_field_body = 1;;
 
 let exterior_rc_header_size = 1;;
-let exterior_gc_header_size = 3;;
+let exterior_gc_header_size = 4;;
 
-let exterior_gc_malloc_return_adjustment = 2;;
+let exterior_gc_malloc_return_adjustment = 3;;
 
 let stk_field_valgrind_id = 0 + 1;;
 let stk_field_limit = stk_field_valgrind_id + 1;;