diff --git a/src/hb-set-private.hh b/src/hb-set-private.hh
index 716881576..9afa3d901 100644
--- a/src/hb-set-private.hh
+++ b/src/hb-set-private.hh
@@ -158,7 +158,7 @@ struct hb_set_t
     }
 
     typedef unsigned long long elt_t;
-    static const unsigned int PAGE_BITS = 1024;
+    static const unsigned int PAGE_BITS = 512;
     static_assert ((PAGE_BITS & ((PAGE_BITS) - 1)) == 0, "");
 
     static inline unsigned int elt_get_min (const elt_t &elt) { return _hb_ctz (elt); }
@@ -183,7 +183,7 @@ struct hb_set_t
   hb_object_header_t header;
   bool successful; /* Allocations successful */
   mutable unsigned int population;
-  hb_vector_t<page_map_t, 8> page_map;
+  hb_vector_t<page_map_t, 1> page_map;
   hb_vector_t<page_t, 1> pages;
 
   inline void init_shallow (void)