diff --git a/README.md b/README.md
index b2e96322..97269402 100644
--- a/README.md
+++ b/README.md
@@ -117,6 +117,21 @@ There may be situations in which you want to ignore a patch supplied by a depend
 }
 ```
 
+## Allowing to force the patch level (-pX)
+
+Some situations require to force the patchLevel used to apply patches on a particular package.
+Its useful for packages like drupal/core which packages only a subdir of the original upstream project on which patches are based.
+
+```json
+{
+  "extra": {
+    "patchLevel": {
+      "drupal/core": "-p2"
+    }
+  }
+}
+```
+
 ## Using patches from HTTP URLs
 
 Composer [blocks](https://getcomposer.org/doc/06-config.md#secure-http) you from downloading anything from HTTP URLs, you can disable this for your project by adding a `secure-http` setting in the config section of your `composer.json`. Note that the `config` section should be under the root of your `composer.json`.