diff --git a/zk-desktop.el b/zk-desktop.el
index 9a468b1..bdd729b 100644
--- a/zk-desktop.el
+++ b/zk-desktop.el
@@ -245,7 +245,7 @@ To quickly change this setting, call `zk-desktop-add-toggle'."
                               (replace-match ""))
                             (when (re-search-forward "]]" end t)
                               (replace-match "")))
-                          (match-string-no-properties 1)))
+                          (match-string-no-properties 0)))
                    (title (buffer-substring-no-properties beg (match-beginning 0)))
                    (new-title (when (member id ids)
                                 (concat zk-desktop-prefix
@@ -264,7 +264,7 @@ To quickly change this setting, call `zk-desktop-add-toggle'."
           (while (re-search-forward zk-id-regexp nil t)
             (let* ((beg (line-beginning-position))
                    (end (line-end-position))
-                   (id (match-string-no-properties 1)))
+                   (id (match-string-no-properties 0)))
               (if (member id ids)
                   (progn
                     (make-text-button beg end
diff --git a/zk-index.el b/zk-index.el
index 2a5581a..0763a60 100644
--- a/zk-index.el
+++ b/zk-index.el
@@ -603,13 +603,12 @@ with query term STRING."
 (defun zk-index--button-at-point-p (&optional pos)
   "Return zk-id when `zk-index' button is at point.
 Takes an option POS position argument."
-  (let ((button (or pos
-                    (button-at (point)))))
+  (let ((button (button-at (or pos (point)))))
     (when (and button
                (button-has-type-p button 'zk-index))
       (save-excursion
-        (re-search-forward zk-id-regexp)
-        (match-string-no-properties 1)))))
+        (when (re-search-forward zk-id-regexp)
+          (match-string-no-properties 0))))))
 
 (defun zk-index-insert-link (&optional id)
   "Insert zk-link in `other-window' for button ID at point."
diff --git a/zk.el b/zk.el
index 32cd9aa..6433c5a 100644
--- a/zk.el
+++ b/zk.el
@@ -124,10 +124,14 @@ If you change this value, set `zk-id-regexp' so that
 the zk IDs can be found."
   :type 'string)
 
-(defcustom zk-id-regexp "\\([0-9]\\{12\\}\\)"
+(defcustom zk-id-regexp "[0-9]\\{12\\}"
   "The regular expression used to search for zk IDs.
 Set it so that it matches strings generated with
-`zk-id-format'."
+`zk-id-format'. The expression should not capture any
+explicitly numbered groups.
+
+See `zk-file-name-regexp' and `zk-link-regexp' functions for
+how this regexp is used."
   :type 'regexp)
 
 (defcustom zk-tag-regexp "\\s#[a-zA-Z0-9]\\+"
@@ -1023,8 +1027,8 @@ Select TAG, with completion, from list of all tags in zk notes."
          (list (split-string files "\n" t))
          (ids (mapcar
                (lambda (x)
-                 (string-match zk-id-regexp x)
-                 (match-string 0 x))
+                 (when (string-match zk-id-regexp x)
+                   (match-string 0 x)))
                list)))
     (delete-dups ids)))