Fix a minor doc syntax typo.
diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 7a3f642..2b9a679 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -404,7 +404,7 @@
if the object type does not provide means to retrieve the size and would
cause a `TypeError`.
- func:`getsizeof` calls the object's __sizeof__ method and adds an additional
+ :func:`getsizeof` calls the object's __sizeof__ method and adds an additional
garbage collector overhead if the object is managed by the garbage collector.
.. versionadded:: 2.6