diff --git a/authserver/authserver/api/serializers.py b/authserver/authserver/api/serializers.py
index b4afe7a..fc59c97 100644
--- a/authserver/authserver/api/serializers.py
+++ b/authserver/authserver/api/serializers.py
@@ -66,7 +66,7 @@ class ProfileSerializer(serializers.HyperlinkedModelSerializer):
         fields = '__all__'
 
     def get_authorized_tools(self, obj):
-        return [tool.slug for tool in models.Tool.objects.filter(course__profile=obj)]
+        return set([tool.slug for tool in models.Tool.objects.filter(course__profile=obj)])
 
 class UserSerializer(serializers.ModelSerializer):
     profile = ProfileSerializer(read_only=True)