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 -r1.118.2.39 -r1.118.2.40
--- openacs-4/packages/acs-tcl/tcl/request-processor-procs.tcl	10 Jan 2017 08:34:28 -0000	1.118.2.39
+++ openacs-4/packages/acs-tcl/tcl/request-processor-procs.tcl	16 Feb 2017 19:33:55 -0000	1.118.2.40
@@ -606,7 +606,10 @@
         return filter_return
     }
 
-    if {[ns_set get [ns_conn headers] Upgrade-Insecure-Requests 0]
+    # ns_set get accepts default as 3rd argument only on Naviserver
+    set upgrade_insecure_requests_p [ns_set get [ns_conn headers] Upgrade-Insecure-Requests]                                     
+    if {$upgrade_insecure_requests_p ne "" &&
+        $upgrade_insecure_requests_p
         && [security::https_available_p]
         && ![security::secure_conn_p]
     } {