Fix typo.
diff --git a/Doc/library/pickle.rst b/Doc/library/pickle.rst
index 1b533f3..73f0611 100644
--- a/Doc/library/pickle.rst
+++ b/Doc/library/pickle.rst
@@ -42,7 +42,7 @@
objects. :mod:`marshal` exists primarily to support Python's :file:`.pyc`
files.
-The :mod:`pickle` module differs from :mod:`marshal` several significant ways:
+The :mod:`pickle` module differs from :mod:`marshal` in several significant ways:
* The :mod:`pickle` module keeps track of the objects it has already serialized,
so that later references to the same object won't be serialized again.