Index: openacs-4/packages/acs-subsite/www/shared/portrait-bits.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-subsite/www/shared/portrait-bits.tcl,v
diff -u -N -r1.13 -r1.14
--- openacs-4/packages/acs-subsite/www/shared/portrait-bits.tcl	3 May 2018 07:18:20 -0000	1.13
+++ openacs-4/packages/acs-subsite/www/shared/portrait-bits.tcl	5 Jul 2018 09:49:33 -0000	1.14
@@ -74,7 +74,16 @@
         #
         if {[file exists $filename]} {
             ns_setexpires 86400 ;# 1 day
-            ad_returnfile_background 200 $itemInfo(mime_type) $filename
+            #
+            # We had "ad_returnfile_background" before, which is a
+            # dependency on xotcl-core. We can use ns_returnfile here
+            # instead. Since a few years NaviServer delivers files via
+            # "ns_returnfile" in the background, when writer_threads
+            # are enabled (which is the case for default
+            # configurations).
+            #
+            ns_returnfile 200 $itemInfo(mime_type) $filename
+
         } else {
             ad_log warning "cannot show portrait with item_id $item_id for user $user_id "
             ns_returnnotfound