diff --git a/src/docs/readme-updater-plugin.js b/src/docs/readme-updater-plugin.js
index 06723fe3b..7865a0cd2 100644
--- a/src/docs/readme-updater-plugin.js
+++ b/src/docs/readme-updater-plugin.js
@@ -49,10 +49,20 @@ export function load (app) {
       }
 
       if (isMonorepoParent) {
+        let project = urlMapping.model.name
+
+        if (project === 'index' && urlMapping.model.parent != null) {
+          project = urlMapping.model.parent?.name
+        }
+
+        if (projects[project] == null) {
+          throw new Error(`Could not derive project name from url mapping model "${urlMapping.model.name}" with parent "${urlMapping.model.parent?.name}"`)
+        }
+
         return {
           comment: urlMapping.model.comment,
-          manifestPath: path.join(projects[urlMapping.model.name].dir, 'package.json'),
-          readmePath: path.join(projects[urlMapping.model.name].dir, 'README.md')
+          manifestPath: path.join(projects[project].dir, 'package.json'),
+          readmePath: path.join(projects[project].dir, 'README.md')
         }
       }