diff --git a/Lib/heapq.py b/Lib/heapq.py
index f3d0669..48697f6 100644
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -351,7 +351,8 @@
     Equivalent to:  sorted(iterable, key=key)[:n]
     """
     in1, in2 = tee(iterable)
-    it = izip(map(key, in1), count(), in2)                  # decorate
+    keys = in1 if key is None else map(key, in1)
+    it = izip(keys, count(), in2)                           # decorate
     result = _nsmallest(n, it)
     return list(map(itemgetter(2), result))                 # undecorate
 
@@ -362,7 +363,8 @@
     Equivalent to:  sorted(iterable, key=key, reverse=True)[:n]
     """
     in1, in2 = tee(iterable)
-    it = izip(map(key, in1), map(neg, count()), in2)        # decorate
+    keys = in1 if key is None else map(key, in1)
+    it = izip(keys, map(neg, count()), in2)                 # decorate
     result = _nlargest(n, it)
     return list(map(itemgetter(2), result))                 # undecorate