diff --git a/cvat/apps/engine/serializers.py b/cvat/apps/engine/serializers.py
index 4f349559..edb96df4 100644
--- a/cvat/apps/engine/serializers.py
+++ b/cvat/apps/engine/serializers.py
@@ -425,7 +425,8 @@ class TaskSerializer(WriteOnceMixin, serializers.ModelSerializer):
                 instance.label_set.all().delete()
             else:
                 for old_label in instance.project.label_set.all():
-                    if new_label_for_name := list(filter(lambda x: x.get('id', None) == old_label.id, labels)):
+                    new_label_for_name = list(filter(lambda x: x.get('id', None) == old_label.id, labels))
+                    if len(new_label_for_name):
                         old_label.name = new_label_for_name[0].get('name', old_label.name)
                     try:
                         new_label = project.label_set.filter(name=old_label.name).first()
@@ -458,7 +459,8 @@ class TaskSerializer(WriteOnceMixin, serializers.ModelSerializer):
             new_label_names = set()
             old_labels = self.instance.project.label_set.all() if self.instance.project_id else self.instance.label_set.all()
             for old_label in old_labels:
-                if len(new_labels := tuple(filter(lambda x: x.get('id') == old_label.id, attrs.get('label_set', [])))):
+                new_labels = tuple(filter(lambda x: x.get('id') == old_label.id, attrs.get('label_set', [])))
+                if len(new_labels):
                     new_label_names.add(new_labels[0].get('name', old_label.name))
                 else:
                     new_label_names.add(old_label.name)