diff --git a/guides/services/constraints.md b/guides/services/constraints.md
index aaa6b0db51..82162a2b18 100644
--- a/guides/services/constraints.md
+++ b/guides/services/constraints.md
@@ -368,13 +368,15 @@ service Sue {
}
```
-In addition to server-side input validation as introduced above, this adds a corresponding `@FieldControl` annotation to the EDMX so that OData / Fiori clients would enforce a valid entry, thereby avoiding unnecessary request roundtrips:
+#### ... in Compositions
+For insert/update, a mandatory value is **not** enforced when the property is missing from the request.
+However, an explicitly provided `null/''` value is validated and rejected. This rule applies to compositions and cascading compositions. To enforce mandatory values, use the [`not null` constraint](../../cds/cdl#constraints) instead.
-```xml
-
-
-
-```
+#### ... in Associations
+
+For insert/update, a mandatory value is **not** enforced when the property is missing from the request. Even an explicitly provided `null/''` value is accepted. To enforce mandatory values, use the [`not null` constraint](../../cds/cdl#constraints) instead.
+
+[Learn more about `@Fieldcontrol` annotation with `@mandatory`.](#mandatory-1){.learn-more}