diff --git a/boards/tests/test_post.py b/boards/tests/test_post.py
--- a/boards/tests/test_post.py
+++ b/boards/tests/test_post.py
@@ -7,7 +7,7 @@ from boards.models import Tag, Post, Thr
 class PostTests(TestCase):
 
     def _create_post(self):
-        tag = Tag.objects.create(name='test_tag')
+        tag, created = Tag.objects.get_or_create(name='test_tag')
         return Post.objects.create_post(title='title', text='text',
                                         tags=[tag])