diff --git a/gnu/packages/gnuzilla.scm b/gnu/packages/gnuzilla.scm
index 9ef8428cc5..07ed2af0bb 100644
--- a/gnu/packages/gnuzilla.scm
+++ b/gnu/packages/gnuzilla.scm
@@ -186,6 +186,10 @@ in the Mozilla clients.")
 (define-public nss
   (package
     (name "nss")
+    ;; FIXME: NSS 3.27.2 fails its tests on armhf. At least some of the test
+    ;; failures appear to be caused by test certificates that have expired.
+    ;; Search the test suite output for 'PayPalEE.cert' for an example:
+    ;; <https://hydra.gnu.org/build/1712083>
     (version "3.27.1")
     (source (origin
               (method url-fetch)