Index: openacs-4/packages/chat/tcl/chat-ajax-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/chat/tcl/chat-ajax-procs.tcl,v
diff -u -N -r1.22 -r1.23
--- openacs-4/packages/chat/tcl/chat-ajax-procs.tcl	24 Oct 2018 10:29:13 -0000	1.22
+++ openacs-4/packages/chat/tcl/chat-ajax-procs.tcl	24 Oct 2018 11:05:08 -0000	1.23
@@ -59,7 +59,7 @@
         {-uid ""}
         msg
     } {
-        if {![chat_room_exists_p [:chat_id]]} {
+        if {![chat_room_exists_p ${:chat_id}]} {
             return
         }
 
@@ -72,7 +72,8 @@
         # This way messages can be persisted immediately every time a
         # message is sent
         if {[:current_message_valid]} {
-            chat_message_post [:chat_id] [:user_id] $msg 1
+            set uid [expr {$uid ne "" ? $uid : ${:user_id}}]
+            chat_message_post ${:chat_id} $uid $msg 1
         }
 
         return $retval