diff --git a/Makefile b/Makefile
index 29c412b..ba00562 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ dev-setup:
 
 .PHONY: tests ## Run unit tests
 tests:
-	py.test graphene_django --cov=graphene_django -vv
+	PYTHONPATH=. py.test graphene_django --cov=graphene_django -vv
 
 .PHONY: format ## Format code
 format: