diff --git a/federation/entities/diaspora/utils.py b/federation/entities/diaspora/utils.py
index 5126680..929cdc9 100644
--- a/federation/entities/diaspora/utils.py
+++ b/federation/entities/diaspora/utils.py
@@ -49,16 +49,16 @@ def get_base_attributes(entity):
     return attributes
 
 
-def get_full_xml_representation(entity, author):
+def get_full_xml_representation(entity, private_key):
     """Get full XML representation of an entity.
 
     This contains the <XML><post>..</post></XML> wrapper.
 
     Accepts either a Base entity or a Diaspora entity.
 
-    Author must have `private_key` that is used in signing certain entities.
+    Author `private_key` must be given so that certain entities can be signed.
     """
     from federation.entities.diaspora.mappers import get_outbound_entity
-    diaspora_entity = get_outbound_entity(entity, author.private_key)
+    diaspora_entity = get_outbound_entity(entity, private_key)
     xml = diaspora_entity.to_xml()
     return "<XML><post>%s</post></XML>" % etree.tostring(xml).decode("utf-8")
diff --git a/federation/tests/entities/diaspora/test_utils.py b/federation/tests/entities/diaspora/test_utils.py
index 445555c..e111325 100644
--- a/federation/tests/entities/diaspora/test_utils.py
+++ b/federation/tests/entities/diaspora/test_utils.py
@@ -1,6 +1,5 @@
 import datetime
 import re
-from unittest.mock import Mock
 
 import arrow
 
@@ -21,7 +20,7 @@ class TestGetBaseAttributes():
 class TestGetFullXMLRepresentation():
     def test_returns_xml_document(self):
         entity = Post()
-        document = get_full_xml_representation(entity, Mock(private_key=""))
+        document = get_full_xml_representation(entity, "")
         document = re.sub(r"<created_at>.*</created_at>", "", document)  # Dates are annoying to compare
         assert document == "<XML><post><status_message><raw_message></raw_message><guid></guid>" \
                            "<diaspora_handle></diaspora_handle><public>false</public>" \