diff --git a/source/guides/migrating-to-pypi-org.rst b/source/guides/migrating-to-pypi-org.rst
index 2b565e8ee..1f16d4365 100644
--- a/source/guides/migrating-to-pypi-org.rst
+++ b/source/guides/migrating-to-pypi-org.rst
@@ -135,6 +135,16 @@ Downloading packages
 
 ``pypi.org`` is the default host for downloading packages.
 
+If downloads still use the old ``pypi.python.org`` host, check whether your
+installer is configured to override its default package index. Configuration
+files, environment variables, and command-line options can all change the
+index used by an installer. Remove or update any override that points at the
+old host, using that installer's documentation to locate its active
+configuration.
+
+For pip, see its :ref:`configuration documentation <pip:config-file>` for the
+supported configuration files, environment variables, and commands.
+
 Managing published packages and releases
 ----------------------------------------