Index: openacs-4/packages/acs-outdated/tcl/acs-tcl-admin-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-outdated/tcl/acs-tcl-admin-procs.tcl,v
diff -u -N -r1.3 -r1.4
--- openacs-4/packages/acs-outdated/tcl/acs-tcl-admin-procs.tcl	7 Aug 2017 23:47:57 -0000	1.3
+++ openacs-4/packages/acs-outdated/tcl/acs-tcl-admin-procs.tcl	1 May 2018 09:06:57 -0000	1.4
@@ -110,7 +110,7 @@
 			    lappend join_clauses "users.user_id = users_charges.user_id"
 			}
 
-			set group_clauses [concat $group_clauses $user_columns]
+			lappend group_clauses {*}$user_columns
 
 			lappend having_clauses "sum(users_charges.amount) > [parameter::get -parameter ExpensiveThreshold]"
 			# only the ones where they haven't paid