diff --git a/src/Composer/Installer/InstallerInterface.php b/src/Composer/Installer/InstallerInterface.php
index e64dfadd2..410fce29b 100644
--- a/src/Composer/Installer/InstallerInterface.php
+++ b/src/Composer/Installer/InstallerInterface.php
@@ -73,7 +73,7 @@ interface InstallerInterface
      * Returns the installation path of a package
      *
      * @param  PackageInterface $package
-     * @return string           path
+     * @return string           path to install to, which MUST not end with a slash
      */
     public function getInstallPath(PackageInterface $package);
 }