diff --git a/mu4e/mu4e-headers.el b/mu4e/mu4e-headers.el
index 158f8671..839381e2 100644
--- a/mu4e/mu4e-headers.el
+++ b/mu4e/mu4e-headers.el
@@ -1073,18 +1073,20 @@ after the end of the search results."
       (+ mu4e~mark-fringe-len (floor (fringe-columns 'left t))) ?\s)
      (mapcar
       (lambda (item)
-        (let* ((field (car item)) (width (cdr item))
+        (let* ( ;; with threading enabled, we're necessarily sorting by date.
+               (sort-field (if mu4e-headers-show-threads :date mu4e-headers-sort-field))
+               (field (car item)) (width (cdr item))
                (info (cdr (assoc field
                                  (append mu4e-header-info mu4e-header-info-custom))))
                (require-full (plist-get info :require-full))
                (sortable (plist-get info :sortable))
                ;; if sortable, it is either t (when field is sortable itself)
                ;; or a symbol (if another field is used for sorting)
-               (sortfield (when sortable (if (booleanp sortable) field sortable)))
+               (this-field (when sortable (if (booleanp sortable) field sortable)))
                (help (plist-get info :help))
                ;; triangle to mark the sorted-by column
                (arrow
-                (when (and sortable (eq sortfield mu4e-headers-sort-field))
+                (when (and sortable (eq this-field sort-field))
                   (if (eq mu4e-headers-sort-direction 'descending) downarrow uparrow)))
                (name (concat (plist-get info :shortname) arrow))
                (map (make-sparse-keymap)))