Index: openacs-4/packages/acs-tcl/tcl/request-processor-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/request-processor-procs.tcl,v
diff -u -N -r1.118.2.15 -r1.118.2.16
--- openacs-4/packages/acs-tcl/tcl/request-processor-procs.tcl	22 May 2016 19:20:40 -0000	1.118.2.15
+++ openacs-4/packages/acs-tcl/tcl/request-processor-procs.tcl	27 May 2016 08:42:20 -0000	1.118.2.16
@@ -890,7 +890,10 @@
         ad_returnredirect [ns_conn url]
         return
     }
-    if {$ad_conn(extra_url) ne "" && ![string match "*$ad_conn(extra_url)" [ns_conn url]]} {
+    if {[info exists ad_conn(extra_url)]
+        && $ad_conn(extra_url) ne ""
+        && ![string match "*$ad_conn(extra_url)" [ns_conn url]]
+    } {
         #
         # On internal redirects, the current ad_conn(extra_url) might be
         # from a previous request, which might have lead to a not-found