diff --git a/src/hb-set.hh b/src/hb-set.hh
index 7ba4c04da..4a7e74b66 100644
--- a/src/hb-set.hh
+++ b/src/hb-set.hh
@@ -368,8 +368,8 @@ struct hb_set_t
     if (!resize (count))
       return;
     population = other->population;
-    memcpy (pages.arrayZ(), other->pages.arrayZ(), count * sizeof (pages.arrayZ()[0]));
-    memcpy (page_map.arrayZ(), other->page_map.arrayZ(), count * sizeof (page_map.arrayZ()[0]));
+    memcpy (pages.arrayZ(), other->pages.arrayZ(), count * sizeof (pages[0]));
+    memcpy (page_map.arrayZ(), other->page_map.arrayZ(), count * sizeof (page_map[0]));
   }
 
   inline bool is_equal (const hb_set_t *other) const