diff --git a/lisp/dired.el b/lisp/dired.el
index 0ccf4b128c4..55c1245b1fa 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -2688,7 +2688,8 @@ name, or the marker and a count of marked files."
   "Pop up buffer BUF in a way suitable for Dired."
   (let ((split-window-preferred-function
 	 (lambda (window)
-	   (or (and (window-splittable-p (selected-window))
+	   (or (and (let ((split-height-threshold 0))
+		      (window-splittable-p (selected-window)))
 		    ;; Try to split the selected window vertically if
 		    ;; that's possible.  (Bug#1806)
 		    (split-window-vertically))