diff --git a/tests/test_annotations.py b/tests/test_annotations.py
index eba7a54..c7b9f0a 100644
--- a/tests/test_annotations.py
+++ b/tests/test_annotations.py
@@ -176,6 +176,7 @@ class PostgreSQLAnnotationTests(unittest.TestCase):
 
     def migrate(self):
         self.s.conn.commit()
+        self.s.conn.close()  # Freeze/checkpoint the fixture, just like a real source migration.
         with redirect_stdout(io.StringIO()):
             return migrate(self.db, self.service, Path(self.tmp.name)/'report.json', schema=self.target, min_free_gib=0)