diff --git a/docs/commands.md b/docs/commands.md
index f18c03e..3b233db 100644
--- a/docs/commands.md
+++ b/docs/commands.md
@@ -51,7 +51,7 @@
 
 If you want to use `glide up` to help you managed dependencies that are checked into your version control consider the flags:
 
-* `--update-vendored` (aliased to `-u`) to update the vendored dependencies.
+* `--update-vendored` (aliased to `-u`) to update the vendored dependencies. If Glide detects a vendored dependency it will update it and leave it in a vendored state. Note, any tertiary dependencies will not be automatically vendored with this flag.
 * `--strip-vcs` (aliased to `-s`) to strip VCS metadata (e.g., `.git` directories) from the `vendor` folder.
 * `--strip-vendor` (aliased to `-v`) to strip nested `vendor/` directories.
 
diff --git a/glide.go b/glide.go
index d00dee4..c69952b 100644
--- a/glide.go
+++ b/glide.go
@@ -485,6 +485,11 @@
 	will be removed when most Godeps users have migrated to using the vendor
 	folder.
 
+	Note, Glide detects vendored dependencies. With the '--update-vendored' flag
+	Glide will update vendored dependencies leaving them in a vendored state.
+	Tertiary dependencies will not be vendored automatically unless the
+	'--strip-vcs' flag is used along with it.
+
 	By default, packages that are discovered are considered transient, and are
 	not stored in the glide.yaml file. The --file=NAME.yaml flag allows you
 	to save the discovered dependencies to a YAML file.