diff --git a/Data/HashMap/Base.hs b/Data/HashMap/Base.hs
index 681b11de..66bd8e97 100644
--- a/Data/HashMap/Base.hs
+++ b/Data/HashMap/Base.hs
@@ -1161,13 +1161,13 @@ filter p = filterWithKey (\_ v -> p v)
 -- | /O(n)/ Return a list of this map's keys.  The list is produced
 -- lazily.
 keys :: HashMap k v -> [k]
-keys = L.map fst . toList
+keys t = build (\ c z -> foldrWithKey (\ k _v ks -> c k ks) z t)
 {-# INLINE keys #-}
 
 -- | /O(n)/ Return a list of this map's values.  The list is produced
 -- lazily.
 elems :: HashMap k v -> [v]
-elems = L.map snd . toList
+elems t = build (\ c z -> foldrWithKey (\ _k v vs -> c v vs) z t)
 {-# INLINE elems #-}
 
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