Index: openacs-4/packages/categories/www/cadmin/master.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/categories/www/cadmin/master.tcl,v
diff -u -r1.12.2.2 -r1.12.2.3
--- openacs-4/packages/categories/www/cadmin/master.tcl	20 Dec 2019 21:18:10 -0000	1.12.2.2
+++ openacs-4/packages/categories/www/cadmin/master.tcl	18 Feb 2021 14:51:14 -0000	1.12.2.3
@@ -16,11 +16,14 @@
 set vars_to_export_list {tree_id category_id }
 
 set set_id [ad_conn form]
-set varname_list [ad_ns_set_keys -exclude {
-  tree_id category_id locale form:mode form:id 
-  __confirmed_p __refreshing_p formbutton:ok
-  __submit_button_name __submit_button_value
-} $set_id]
+set varname_list [lmap k [dict keys [ns_set array $set_id]] {
+    if {$k in {
+        tree_id category_id locale form:mode form:id 
+        __confirmed_p __refreshing_p formbutton:ok
+        __submit_button_name __submit_button_value
+    }} continue
+    set k
+}]
 
 foreach name $varname_list {
   set $name [ns_set get $set_id $name]