diff --git a/Headers/gnustep/base/NSAutoreleasePool.h b/Headers/gnustep/base/NSAutoreleasePool.h
index da79e0376..8576cfee2 100644
--- a/Headers/gnustep/base/NSAutoreleasePool.h
+++ b/Headers/gnustep/base/NSAutoreleasePool.h
@@ -26,6 +26,8 @@
 
 #include <gnustep/base/preface.h>
 
+/* Each pool holds its objects-to-be-released in a linked-list of 
+   these structures. */
 struct autorelease_array_list
 {
   struct autorelease_array_list *next;
@@ -34,6 +36,15 @@ struct autorelease_array_list
   id objects[0];
 };
 
+/* This structure holds a per-thread cache of NSAutoreleasePool objects,
+   so they don't have to be alloc/dealloc'ed each time. */
+struct autorelease_cache
+{
+  id *cache;
+  int cache_size;
+  int cache_count;
+};
+
 @interface NSAutoreleasePool : NSObject 
 {
   /* For re-setting the current pool when we are dealloc'ed. */