Index: openacs-4/packages/categories/www/cadmin/tree-order-update.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/categories/www/cadmin/tree-order-update.tcl,v
diff -u -N -r1.9 -r1.10
--- openacs-4/packages/categories/www/cadmin/tree-order-update.tcl	25 Apr 2018 19:47:46 -0000	1.9
+++ openacs-4/packages/categories/www/cadmin/tree-order-update.tcl	1 May 2018 09:06:57 -0000	1.10
@@ -52,7 +52,7 @@
             ## put category and all children back on stack
             set next [lreplace $next 2 2 $count]
             set stack [linsert $stack 0 $next]
-            set stack [concat [lsort -integer -index 0 $child($act_category)] $stack]
+            set stack [linsert $stack 0 [lsort -integer -index 0 $child($act_category)]]
         } else {
             ## this category has no children, so it is done
             lappend done_list [list $act_category $count [expr {$count + 1}]]