diff --git a/apps/documents/models.py b/apps/documents/models.py
index 2d8de2ef4c..3de23c3f52 100644
--- a/apps/documents/models.py
+++ b/apps/documents/models.py
@@ -66,7 +66,7 @@ class DocumentType(models.Model):
     def __unicode__(self):
         return self.name
 
-   def natural_key(self):
+    def natural_key(self):
         return (self.name,)
 
     class Meta: