diff --git a/envsetup.sh b/envsetup.sh
index 1907e4c..74cfbbd 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -1084,6 +1084,14 @@
     echo "can't find Android.mk"
 }
 
+# Ensure that we're always using the adb in the tree. This works around the fact
+# that bash caches $PATH lookups, so if you use adb before lunching/building the
+# one in your tree, you'll continue to get /usr/bin/adb or whatever even after
+# you have the one from your current tree on your path. Historically this would
+# cause confusion because glinux had adb in /usr/bin/ by default, though that
+# doesn't appear to be the case on my rodete hosts; it is however still the case
+# that my Mac has /usr/local/bin/adb installed by default and on the default
+# path.
 function adb() {
     local ADB=$(which adb)
     if [ -z "$ADB" ]; then