diff --git a/Lib/functools.py b/Lib/functools.py
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -142,7 +142,7 @@
     # to allow the implementation to change (including a possible C version).
 
     def decorating_function(user_function,
-                tuple=tuple, sorted=sorted, len=len, KeyError=KeyError):
+                tuple=tuple, sorted=sorted, len=len):
 
         hits = misses = 0
         kwd_mark = (object(),)          # separates positional and keyword args
@@ -157,10 +157,10 @@
                 key = args
                 if kwds:
                     key += kwd_mark + tuple(sorted(kwds.items()))
-                try:
+                if key in cache:
                     result = cache[key]
                     hits += 1
-                except KeyError:
+                else:
                     result = user_function(*args, **kwds)
                     cache[key] = result
                     misses += 1
@@ -176,12 +176,12 @@
                 key = args
                 if kwds:
                     key += kwd_mark + tuple(sorted(kwds.items()))
-                try:
+                if key in cache:
                     with lock:
                         result = cache[key]
                         cache_renew(key)        # record recent use of this key
                         hits += 1
-                except KeyError:
+                else:
                     result = user_function(*args, **kwds)
                     with lock:
                         cache[key] = result     # record recent use of this key
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -718,6 +718,16 @@
         self.assertEqual(fib.cache_info(),
             functools._CacheInfo(hits=0, misses=0, maxsize=None, currsize=0))
 
+    def test_lru_with_exceptions(self):
+        for maxsize in (None, 100):
+            @functools.lru_cache(maxsize)
+            def func(i):
+                return 'abc'[i]
+            self.assertEqual(func(0), 'a')
+            with self.assertRaises(IndexError) as cm:
+                func(15)
+            self.assertIsNone(cm.exception.__context__)
+
 def test_main(verbose=None):
     test_classes = (
         TestPartial,