diff --git a/Doc/library/timeit.rst b/Doc/library/timeit.rst
index bad7194..5cb174c 100644
--- a/Doc/library/timeit.rst
+++ b/Doc/library/timeit.rst
@@ -224,7 +224,7 @@
 
 .. cmdoption:: -u, --unit=U
 
-    specify a time unit for timer output; can select usec, msec, or sec
+    specify a time unit for timer output; can select nsec, usec, msec, or sec
 
    .. versionadded:: 3.5
 
diff --git a/Lib/test/test_timeit.py b/Lib/test/test_timeit.py
index b297222..4e8c118 100644
--- a/Lib/test/test_timeit.py
+++ b/Lib/test/test_timeit.py
@@ -331,7 +331,7 @@
             invalid = self.run_main(seconds_per_increment=0.002,
                     switches=['-u', 'parsec'])
         self.assertEqual(error_stringio.getvalue(),
-                    "Unrecognized unit. Please select usec, msec, or sec.\n")
+                    "Unrecognized unit. Please select nsec, usec, msec, or sec.\n")
 
     def test_main_exception(self):
         with captured_stderr() as error_stringio:
diff --git a/Lib/timeit.py b/Lib/timeit.py
index 8bc6a9e..23bdd02 100644
--- a/Lib/timeit.py
+++ b/Lib/timeit.py
@@ -18,7 +18,7 @@
                 Execution time of this setup statement is NOT timed.
   -p/--process: use time.process_time() (default is time.perf_counter())
   -v/--verbose: print raw timing results; repeat for more digits precision
-  -u/--unit: set the output time unit (usec, msec, or sec)
+  -u/--unit: set the output time unit (nsec, usec, msec, or sec)
   -h/--help: print this usage message and exit
   --: separate options from statement, use when statement starts with -
   statement: statement to be timed (default 'pass')
@@ -272,7 +272,7 @@
     repeat = default_repeat
     verbose = 0
     time_unit = None
-    units = {"usec": 1e-6, "msec": 1e-3, "sec": 1.0}
+    units = {"nsec": 1e-9, "usec": 1e-6, "msec": 1e-3, "sec": 1.0}
     precision = 3
     for o, a in opts:
         if o in ("-n", "--number"):
@@ -283,7 +283,7 @@
             if a in units:
                 time_unit = a
             else:
-                print("Unrecognized unit. Please select usec, msec, or sec.",
+                print("Unrecognized unit. Please select nsec, usec, msec, or sec.",
                     file=sys.stderr)
                 return 2
         if o in ("-r", "--repeat"):