diff --git a/abl/reasoning/reasoner.py b/abl/reasoning/reasoner.py
index 6d35729..7e3af8a 100644
--- a/abl/reasoning/reasoner.py
+++ b/abl/reasoning/reasoner.py
@@ -76,7 +76,7 @@ class Reasoner:
         if isinstance(dist_func, str):
             if dist_func not in ["hamming", "confidence", "avg_confidence"]:
                 raise NotImplementedError(
-                    'Valid options for predefined dist_func include "hamming" '
+                    'Valid options for predefined dist_func include "hamming", '
                     + f'"confidence" and "avg_confidence", but got {dist_func}.'
                 )
             return
diff --git a/tests/test_reasoning.py b/tests/test_reasoning.py
index d3a08b6..04b1f84 100644
--- a/tests/test_reasoning.py
+++ b/tests/test_reasoning.py
@@ -114,8 +114,10 @@ class TestReaonser(object):
     def test_invalid_predefined_dist_func(self, kb_add):
         with pytest.raises(NotImplementedError) as excinfo:
             Reasoner(kb_add, "invalid_dist_func")
-        assert 'Valid options for predefined dist_func include "hamming" and "confidence"' in str(
-            excinfo.value
+        assert (
+            'Valid options for predefined dist_func include "hamming", "confidence" '
+            + 'and "avg_confidence"'
+            in str(excinfo.value)
         )
 
     def random_dist(self, data_example, candidates, candidate_idxs, reasoning_results):