diff --git a/src/racket/gc2/newgc.c b/src/racket/gc2/newgc.c
index 6f12a37ff6..bea1e8b0d7 100644
--- a/src/racket/gc2/newgc.c
+++ b/src/racket/gc2/newgc.c
@@ -2839,6 +2839,7 @@ static NewGC *init_type_tags_worker(NewGC *inheritgc, NewGC *parentgc,
   initialize_signal_handler(gc);
   GC_add_roots(&gc->park, (char *)&gc->park + sizeof(gc->park) + 1);
   GC_add_roots(&gc->park_save, (char *)&gc->park_save + sizeof(gc->park_save) + 1);
+  GC_add_roots(&gc->park_isave, (char *)&gc->park_isave + sizeof(gc->park_isave) + 1);
 
   return gc;
 }
@@ -4544,6 +4545,29 @@ void print_debug_stats(NewGC *gc) {
 }
 #endif
 
+static void park_for_inform_callback(NewGC *gc)
+{
+  /* Avoid nested collections, which would need
+     nested parking spaces: */
+  gc->dumping_avoid_collection++;
+
+  /* Inform might allocate, which might need park: */
+  gc->park_isave[0] = gc->park[0];
+  gc->park_isave[1] = gc->park[1];
+  gc->park[0] = NULL;
+  gc->park[1] = NULL;
+}
+
+static void unpark_for_inform_callback(NewGC *gc)
+{
+  gc->park[0] = gc->park_isave[0];
+  gc->park[1] = gc->park_isave[1];
+  gc->park_isave[0] = NULL;
+  gc->park_isave[1] = NULL;
+  
+  --gc->dumping_avoid_collection;
+}
+
 #if 0
 extern double scheme_get_inexact_milliseconds(void);
 # define TIME_DECLS() double start, task_start
@@ -4788,25 +4812,12 @@ static void garbage_collect(NewGC *gc, int force_full, int switching_master, Log
 #ifdef MZ_USE_PLACES
     is_master = (gc == MASTERGC);
 #endif
-    gc->dumping_avoid_collection++;
-
-    /* Inform might allocate, which might need park: */
-    gc->park_save[0] = gc->park[0];
-    gc->park_save[1] = gc->park[1];
-    gc->park[0] = NULL;
-    gc->park[1] = NULL;
-
+    park_for_inform_callback(gc);
     gc->GC_collect_inform_callback(is_master, gc->gc_full, 
                                    old_mem_use + old_gen0, gc->memory_in_use, 
                                    old_mem_allocated, mmu_memory_allocated(gc->mmu),
                                    gc->child_gc_total);
-
-    gc->park[0] = gc->park_save[0];
-    gc->park[1] = gc->park_save[1];
-    gc->park_save[0] = NULL;
-    gc->park_save[1] = NULL;
-
-    --gc->dumping_avoid_collection;
+    unpark_for_inform_callback(gc);
   }
 #ifdef MZ_USE_PLACES
   if (lmi) {
@@ -4880,10 +4891,12 @@ static void garbage_collect(NewGC *gc, int force_full, int switching_master, Log
       wait_if_master_in_progress(gc, &sub_lmi);
       if (sub_lmi.ran) {
         if (gc->GC_collect_inform_callback) {
+          park_for_inform_callback(gc);
           gc->GC_collect_inform_callback(1, sub_lmi.full,
                                          sub_lmi.pre_used, sub_lmi.post_used,
                                          sub_lmi.pre_admin, sub_lmi.post_admin,
                                          0);
+          unpark_for_inform_callback(gc);
         }
       }
     }
diff --git a/src/racket/gc2/newgc.h b/src/racket/gc2/newgc.h
index cbb8a7362b..8d9ab5502e 100644
--- a/src/racket/gc2/newgc.h
+++ b/src/racket/gc2/newgc.h
@@ -226,6 +226,7 @@ typedef struct NewGC {
 
   void *park[2];
   void *park_save[2];
+  void *park_isave[2];
 
   unsigned short weak_array_tag;
   unsigned short weak_box_tag;