diff --git a/AdvancedInstall.md b/AdvancedInstall.md
index 1b51330..beb907e 100644
--- a/AdvancedInstall.md
+++ b/AdvancedInstall.md
@@ -77,6 +77,9 @@ tree for running-in-place. This basically does a
 executable knows that it adds this directory to PYTHONPATH before it
 does anything else.
 
+If you need to use an HTTP proxy to access the web, set the `http_proxy`
+environment variable accordingly. For example in Unix: `http_proxy=`host:port` python setup.py build`.
+
 After building, you can run the source tree's `bin/tahoe` script to
 create, configure, and use your new Tahoe-LAFS node. As long as `bin/tahoe` is
 left inside the built source tree, it can be run from anywhere (even through a