diff --git a/UPGRADE.md b/UPGRADE.md
index 9620aa4028..50dd0e46a4 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -390,4 +390,9 @@ class ExtensionErrorHandler implements ErrorHandler
 }
 ```
 
+### Update `mll-lab/graphql-php-scalars`
+
+If you depend on `mll-lab/graphql-php-scalars`, please upgrade it.  
+Now the minimal required version is v4.
+
 You can now discard errors by returning `null` from the handler.