diff --git a/AdvancedInstall.md b/AdvancedInstall.md
index 6cb6b1e..eea6984 100644
--- a/AdvancedInstall.md
+++ b/AdvancedInstall.md
@@ -34,7 +34,7 @@ step.
 
 `python setup.py build` will download and build any third-party libraries that
 are not already available on your system. It will also prepare the source
-tree for running-in-place. Thios basically does a
+tree for running-in-place. This basically does a
 "`setup.py develop`" into a local
 `./support/lib/python2.5/site-packages/` directory. The `bin/tahoe`
 executable knows that it adds this directory to PYTHONPATH before it