--- ../tlshell.tcl.orig	2020-05-01 17:29:18.643000616 +0200
+++ ./texmf-dist/scripts/tlshell/tlshell.tcl	2020-05-01 17:29:38.669640826 +0200
@@ -1546,7 +1546,7 @@
     tk_messageBox -message [__ "No backup directory defined"]
     return
   }
-  set bdir [file join [exec kpsewhich -var-value SELFAUTOPARENT] $bdir]
+  set bdir [file join [exec kpsewhich -var-value TEXMFROOT] $bdir]
   if {! [file isdirectory $bdir]} {
     tk_messageBox -message [__ "Backup directory %s does not exist" $bdir]
     return