diff --git a/src/mzscheme/src/struct.c b/src/mzscheme/src/struct.c
index 940250f835..b60db7af6f 100644
--- a/src/mzscheme/src/struct.c
+++ b/src/mzscheme/src/struct.c
@@ -4788,6 +4788,7 @@ static void register_traversers(void)
   GC_REG_TRAV(scheme_rt_struct_proc_info, mark_struct_proc_info);
 
   GC_REG_TRAV(scheme_chaperone_type, mark_chaperone);
+  GC_REG_TRAV(scheme_proc_chaperone_type, mark_chaperone);
 }
 
 END_XFORM_SKIP;