diff --git a/README.md b/README.md
index e7f129dc..565a2dfb 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,8 @@ You can also install `composer-unused` as a local __development__ dependency:
 ## Usage
 Depending on the kind of your installation the command might differ.
 
+*Note: Packages must installed via `composer install` or `composer update` prior to running `composer-unused`.*
+
 ### PHAR
 The `phar` archive can be run directly in you project: