diff --git a/tests/data/test1660 b/tests/data/test1660
index 76df04f1e..3ddd8d427 100644
--- a/tests/data/test1660
+++ b/tests/data/test1660
@@ -71,7 +71,7 @@ expire.example [expire.example]: 1548369268
 'expire.example' is not HSTS
 'expire.example' is not HSTS
 </stdout>
-<file name="log/hsts%TESTNUMBER">
+<file name="log/hsts%TESTNUMBER" mode="text">
 # Your HSTS cache. https://curl.se/docs/hsts.html
 # This file was generated by libcurl! Edit at your own risk.
 .example.com "20191001 04:47:41"