diff --git a/src/mzscheme/gc2/mem_account.c b/src/mzscheme/gc2/mem_account.c
index ae4d27df2c..9dd94cb0be 100644
--- a/src/mzscheme/gc2/mem_account.c
+++ b/src/mzscheme/gc2/mem_account.c
@@ -338,7 +338,14 @@ inline static void mark_normal_obj(NewGC *gc, int type, void *ptr)
                            ignore them outright. In the case of custodians, we do need
                            to do the check; those differences are handled by replacing
                            the mark procedure in mark_table. */
-                        gc->mark_table[*(unsigned short*)ptr](ptr);
+                        unsigned short tag = *(unsigned short*)ptr;
+                        ASSERT_TAG(tag);
+                        if((unsigned long)gc->mark_table[tag] < PAGE_TYPES) {
+                          /* atomic */
+                        } else {
+                          GC_ASSERT(mark_table[tag]);
+                          gc->mark_table[tag](ptr);
+                        }
                         break;
                       }
     case PAGE_ATOMIC: break;
@@ -403,6 +410,12 @@ static void propagate_accounting_marks(NewGC *gc)
   PageMap pagemap = gc->page_maps;
   while(pop_ptr(&p) && !gc->kill_propagation_loop) {
     page = pagemap_find_page(pagemap, p);
+#ifdef MZ_USE_PLACES
+    if (!page) {
+      page = pagemap_find_page(MASTERGC->page_maps, p);
+    }
+#endif
+    GC_ASSERT(page);
     set_backtrace_source(p, page->page_type);
     GCDEBUG((DEBUGOUTF, "btc_account: popped off page %p:%p, ptr %p\n", page, page->addr, p));
     if(page->size_class) {
diff --git a/src/mzscheme/gc2/newgc.c b/src/mzscheme/gc2/newgc.c
index 5ca281e6f4..01f571856a 100644
--- a/src/mzscheme/gc2/newgc.c
+++ b/src/mzscheme/gc2/newgc.c
@@ -1483,7 +1483,7 @@ inline static void mark_stack_initialize() {
 
 inline static void push_ptr(void *ptr)
 {
-  /* This happens during propoagation if we go past the end of this MarkSegment*/
+  /* This happens during propagation if we go past the end of this MarkSegment*/
   if(mark_stack->top == MARK_STACK_END(mark_stack)) {
     /* test to see if we already have another stack page ready */
     if(mark_stack->next) {
diff --git a/src/mzscheme/src/module.c b/src/mzscheme/src/module.c
index a75aabd97f..6169e83f2a 100644
--- a/src/mzscheme/src/module.c
+++ b/src/mzscheme/src/module.c
@@ -4071,7 +4071,7 @@ static void start_module(Scheme_Module *m, Scheme_Env *env, int restart,
   Scheme_Object *l, *new_cycle_list;
   int prep_namespace = 0;
 
-  if (SAME_OBJ(m, kernel))
+  if (is_builtin_modname(m->modname))
     return;
 
   for (l = cycle_list; !SCHEME_NULLP(l); l = SCHEME_CDR(l)) {