diff --git a/composer.json b/composer.json
index 9c70a45..5d38a58 100644
--- a/composer.json
+++ b/composer.json
@@ -11,6 +11,7 @@
 	},
 	"require": {
 		"php": ">=5.3.0",
+		"wikibase/data-model": "~4.1",
 		"wikibase/data-model-services": "~1.1"
 	},
 	"require-dev": {