diff --git a/doc/articles/custom-installers.md b/doc/articles/custom-installers.md
index fdc6f84c0..9c0ee2b65 100644
--- a/doc/articles/custom-installers.md
+++ b/doc/articles/custom-installers.md
@@ -149,6 +149,7 @@ source for the exact signature):
   when the package needs to be removed.
 * **getInstallPath()**, this method should return the location where the
   package is to be installed, _relative from the location of composer.json._
+  The path _must not end with a slash._
 
 Example: