diff --git a/treeherder/model/models.py b/treeherder/model/models.py
index <HASH>..<HASH> 100644
--- a/treeherder/model/models.py
+++ b/treeherder/model/models.py
@@ -815,8 +815,9 @@ class JobNote(models.Model):
             return
 
         for bug_number in add_bugs:
-            classification, _ = text_log_error.set_classification("ManualDetector",
-                                                                  bug_number=bug_number)
+            classification, _ = ClassifiedFailure.objects.get_or_create(bug_number=bug_number)
+            classification, _ = text_log_error.set_classification("ManualDetector", classification)
+
         if len(add_bugs) == 1 and not existing_bugs:
             text_log_error.mark_best_classification_verified(classification)
 
@@ -1193,13 +1194,9 @@ class TextLogError(models.Model):
                 .first())
 
     @transaction.atomic
-    def set_classification(self, matcher_name, classification=None, bug_number=None):
+    def set_classification(self, matcher_name, classification):
         if classification is None:
-            if bug_number:
-                classification, _ = ClassifiedFailure.objects.get_or_create(
-                    bug_number=bug_number)
-            else:
-                classification = ClassifiedFailure.objects.create()
+            classification = ClassifiedFailure.objects.create()
 
         match = TextLogErrorMatch.objects.create(
             text_log_error=self,
Create ClassifiedFailures from bugs only where necessary

Since ClassifiedFailures are only created from a bug number in one place
we can make set_classification more specific by pulling that
functionality out to where the bug numbers are handled.