diff --git a/ANNOUNCE b/ANNOUNCE
index b67bcaaea..de38849eb 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -142,10 +142,18 @@ sha256sum < groff-1.23.0.rc4.tar.gz | cut -f1 -d\  | xxd -r -p | base64
 Caveats
 =======
 
-o A defect in GNU diffutils 3.9 (January 2023) causes gdiffmk to
+o Some portability issues are known to affect groff's gdiffmk utility.
+
+  A defect in GNU diffutils 3.9 (January 2023) causes gdiffmk to
   malfunction and its automated test to fail.  See
   <https://debbugs.gnu.org/db/61/61193.html>.
 
+  gdiffmk does not work with BusyBox diff (which does not implement GNU
+  diff's "-D" option).
+
+  gdiffmk does not work on FreeBSD due to specifics of that platform's
+  expr(1) implementation.
+
 o GNU tools, or otherwise POSIX-conforming ones, are generally required
   to build on Solaris 10 or 11.  See the "PROBLEMS" file in the
   distribution archive.