diff --git a/sqlite_utils/db.py b/sqlite_utils/db.py
index ef8c40e..f524e13 100644
--- a/sqlite_utils/db.py
+++ b/sqlite_utils/db.py
@@ -368,7 +368,7 @@ class Database:
             pm.hook.prepare_connection(conn=self.conn)
         self.strict = strict
 
-    def close(self):
+    def close(self) -> None:
         "Close the SQLite connection, and the underlying database file"
         self.conn.close()