diff --git a/spacy/tests/serialize/test_serialize_kb.py b/spacy/tests/serialize/test_serialize_kb.py
index bcf27990b..26e912738 100644
--- a/spacy/tests/serialize/test_serialize_kb.py
+++ b/spacy/tests/serialize/test_serialize_kb.py
@@ -29,14 +29,14 @@ def test_serialize_kb_disk(en_vocab):
 def _get_dummy_kb(vocab):
     kb = KnowledgeBase(vocab=vocab, entity_vector_length=3)
 
-    kb.add_entity(entity="Q53", prob=0.33, entity_vector=[0, 5, 3])
-    kb.add_entity(entity="Q17", prob=0.2, entity_vector=[7, 1, 0])
-    kb.add_entity(entity="Q007", prob=0.7, entity_vector=[0, 0, 7])
-    kb.add_entity(entity="Q44", prob=0.4, entity_vector=[4, 4, 4])
+    kb.add_entity(entity=u'Q53', prob=0.33, entity_vector=[0, 5, 3])
+    kb.add_entity(entity=u'Q17', prob=0.2, entity_vector=[7, 1, 0])
+    kb.add_entity(entity=u'Q007', prob=0.7, entity_vector=[0, 0, 7])
+    kb.add_entity(entity=u'Q44', prob=0.4, entity_vector=[4, 4, 4])
 
-    kb.add_alias(alias="double07", entities=["Q17", "Q007"], probabilities=[0.1, 0.9])
-    kb.add_alias(alias="guy", entities=["Q53", "Q007", "Q17", "Q44"], probabilities=[0.3, 0.3, 0.2, 0.1])
-    kb.add_alias(alias="random", entities=["Q007"], probabilities=[1.0])
+    kb.add_alias(alias=u'double07', entities=[u'Q17', u'Q007'], probabilities=[0.1, 0.9])
+    kb.add_alias(alias=u'guy', entities=[u'Q53', u'Q007', u'Q17', u'Q44'], probabilities=[0.3, 0.3, 0.2, 0.1])
+    kb.add_alias(alias=u'random', entities=[u'Q007'], probabilities=[1.0])
 
     return kb
 
@@ -44,30 +44,30 @@ def _get_dummy_kb(vocab):
 def _check_kb(kb):
     # check entities
     assert kb.get_size_entities() == 4
-    for entity_string in ["Q53", "Q17", "Q007", "Q44"]:
+    for entity_string in [u'Q53', u'Q17', u'Q007', u'Q44']:
         assert entity_string in kb.get_entity_strings()
-    for entity_string in ["", "Q0"]:
+    for entity_string in [u'', u'Q0']:
         assert entity_string not in kb.get_entity_strings()
 
     # check aliases
     assert kb.get_size_aliases() == 3
-    for alias_string in ["double07", "guy", "random"]:
+    for alias_string in [u'double07', u'guy', u'random']:
         assert alias_string in kb.get_alias_strings()
-    for alias_string in ["nothingness", "", "randomnoise"]:
+    for alias_string in [u'nothingness', u'', u'randomnoise']:
         assert alias_string not in kb.get_alias_strings()
 
     # check candidates & probabilities
-    candidates = sorted(kb.get_candidates("double07"), key=lambda x: x.entity_)
+    candidates = sorted(kb.get_candidates(u'double07'), key=lambda x: x.entity_)
     assert len(candidates) == 2
 
-    assert candidates[0].entity_ == "Q007"
+    assert candidates[0].entity_ == u'Q007'
     assert 0.6999 < candidates[0].entity_freq < 0.701
     assert candidates[0].entity_vector == [0, 0, 7]
-    assert candidates[0].alias_ == "double07"
+    assert candidates[0].alias_ == u'double07'
     assert 0.899 < candidates[0].prior_prob < 0.901
 
-    assert candidates[1].entity_ == "Q17"
+    assert candidates[1].entity_ == u'Q17'
     assert 0.199 < candidates[1].entity_freq < 0.201
     assert candidates[1].entity_vector == [7, 1, 0]
-    assert candidates[1].alias_ == "double07"
+    assert candidates[1].alias_ == u'double07'
     assert 0.099 < candidates[1].prior_prob < 0.101