Index: openacs-4/packages/chat/tcl/chat-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/chat/tcl/chat-procs.tcl,v
diff -u -N -r1.11.6.8 -r1.11.6.9
--- openacs-4/packages/chat/tcl/chat-procs.tcl	21 Apr 2017 20:21:49 -0000	1.11.6.8
+++ openacs-4/packages/chat/tcl/chat-procs.tcl	9 May 2017 16:09:13 -0000	1.11.6.9
@@ -605,7 +605,8 @@
 	    set contents [list]
             foreach message [db_list_of_lists get_archives_messages {}] {
 		lassign $message msg creation_user creation_date
-                lappend contents "\[$creation_date\] <b>[chat_user_name $creation_user]</b>: $msg"
+                set user_name [expr {$creation_user > 0 ? [chat_user_name $creation_user] : "system"}]
+                lappend contents "\[$creation_date\] <b>${user_name}</b>: $msg"
             }
             if { $contents ne "" } {
 		set today [clock format [clock seconds] -format "%d.%m.%Y"]