diff --git a/federation/entities/diaspora/mappers.py b/federation/entities/diaspora/mappers.py
index dcdd86f..5578005 100644
--- a/federation/entities/diaspora/mappers.py
+++ b/federation/entities/diaspora/mappers.py
@@ -206,7 +206,7 @@ def get_outbound_entity(entity, private_key):
         outbound = DiasporaRetraction.from_base(entity)
     if not outbound:
         raise ValueError("Don't know how to convert this base entity to Diaspora protocol entities.")
-    if issubclass(cls, DiasporaRelayableMixin) and not outbound.signature:
+    if isinstance(outbound, DiasporaRelayableMixin) and not outbound.signature:
         # Sign by author if not signed yet. We don't want to overwrite any existing signature in the case
         # that this is being sent by the parent author
         outbound.sign(private_key)
diff --git a/federation/tests/entities/diaspora/test_mappers.py b/federation/tests/entities/diaspora/test_mappers.py
index 04636a6..0dddc99 100644
--- a/federation/tests/entities/diaspora/test_mappers.py
+++ b/federation/tests/entities/diaspora/test_mappers.py
@@ -221,3 +221,9 @@ class TestGetOutboundEntity(object):
     def test_retraction_is_converted_to_diasporaretraction(self):
         entity = Retraction()
         assert isinstance(get_outbound_entity(entity, get_dummy_private_key()), DiasporaRetraction)
+
+    def test_signs_relayable_if_no_signature(self):
+        entity = DiasporaComment()
+        dummy_key = get_dummy_private_key()
+        outbound = get_outbound_entity(entity, dummy_key)
+        assert outbound.signature != ""