Fix grammar.
diff --git a/Doc/install/index.rst b/Doc/install/index.rst
index 2231058..0336551 100644
--- a/Doc/install/index.rst
+++ b/Doc/install/index.rst
@@ -314,8 +314,8 @@
stash of Python modules. This scheme's name is derived from the idea of a
"home" directory on Unix, since it's not unusual for a Unix user to make their
home directory have a layout similar to :file:`/usr/` or :file:`/usr/local/`.
-This scheme can be used by anyone, regardless of the operating system their
-installing for.
+This scheme can be used by anyone, regardless of the operating system they
+are installing for.
Installing a new module distribution is as simple as ::