diff --git a/pkg/ottl/contexts/ottlspanevent/span_events.go b/pkg/ottl/contexts/ottlspanevent/span_events.go
index 69fea44c6968..a9f41b1c60ea 100644
--- a/pkg/ottl/contexts/ottlspanevent/span_events.go
+++ b/pkg/ottl/contexts/ottlspanevent/span_events.go
@@ -357,7 +357,7 @@ func accessSpanEventIndex() ottl.StandardGetSetter[TransformContext] {
 			return tCtx.eventIndex, nil
 		},
 		Setter: func(_ context.Context, _ TransformContext, _ any) error {
-			return nil
+			return errors.New("the 'event_index' path cannot be modified")
 		},
 	}
 }