atom: use valid characters for idHEADmaster

1 files changed, 2 insertions, 1 deletions

diff --git a/src/atom.scm b/src/atom.scm
index c1428ec..6e7a8b2 100644
--- a/src/atom.scm
+++ b/src/atom.scm
@@ -96,9 +96,10 @@
                        (contributors '())
                        (media '())
                  #:allow-other-keys)
+  (define valid (char-set-intersection char-set:ascii char-set:letter))
   (define (id-from-title title)
     (string-map (lambda (c)
-                  (if (char-set-contains? char-set:letter c) c #\-))
+                  (if (char-set-contains? valid c) c #\-))
                 title))
 
   (%make-entry (or id (id-from-title title))