diff --git a/tests/substitute.scm b/tests/substitute.scm
index 542aaf603f..1827ffe8d4 100644
--- a/tests/substitute.scm
+++ b/tests/substitute.scm
@@ -178,10 +178,10 @@ a file for NARINFO."
         (call-with-output-file
             (string-append narinfo-directory "/example.nar")
           (cute write-file
-                (string-append narinfo-directory "/example.out") <>))
-
-        (%allow-unauthenticated-substitutes? #f))
-      thunk
+                (string-append narinfo-directory "/example.out") <>)))
+      (lambda ()
+        (mock ((guix narinfo) valid-narinfo?) (const #t)
+              (thunk)))
       (lambda ()
         (when (file-exists? cache-directory)
           (delete-file-recursively cache-directory))))))