Index: openacs-4/packages/acs-tcl/tcl/form-processing-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/form-processing-procs.tcl,v
diff -u -r1.87.2.5 -r1.87.2.6
--- openacs-4/packages/acs-tcl/tcl/form-processing-procs.tcl	5 Jul 2019 10:00:54 -0000	1.87.2.5
+++ openacs-4/packages/acs-tcl/tcl/form-processing-procs.tcl	27 Aug 2019 09:56:17 -0000	1.87.2.6
@@ -806,12 +806,13 @@
         }
     }
 
-    # Antonio Pisano: export property will eventually end up into
-    # template::form::render, where export_vars will take care of
-    # creating the required hidden form fields according to
-    # specification.
+    # Use export_vars to serialize variables from -export flag as
+    # hidden form fields. We need to do it now rather than later in
+    # the rendering, as only now the uplevel variables come from is
+    # well known.
     if { [info exists export] } {
-        template::form::set_properties $form_name export $export
+        template::form::set_properties $form_name exported_vars \
+            [uplevel [list export_vars -form $export]]
     }
 
     # We need to track these for submission time and for error checking
Index: openacs-4/packages/acs-templating/tcl/form-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-templating/tcl/form-procs.tcl,v
diff -u -r1.59 -r1.59.2.1
--- openacs-4/packages/acs-templating/tcl/form-procs.tcl	28 Dec 2018 11:24:10 -0000	1.59
+++ openacs-4/packages/acs-templating/tcl/form-procs.tcl	27 Aug 2019 09:56:17 -0000	1.59.2.1
@@ -633,12 +633,11 @@
         append output "<legend>$fieldset_legend</legend>"
     }
 
-    # Export variables specified by the export property as hidden
-    # formfields. (used e.g. by ad_form when specifying the -export
-    # flag)
-    if { [info exists form_properties(export)] } {
+    # Include exported variables created by ad_form when specifying
+    # the -export flag
+    if { [info exists form_properties(exported_vars)] } {
         append output {<!-- Exported form vars START -->}
-        append output [uplevel #$level [subst {export_vars -form {$form_properties(export)}}]]
+        append output $form_properties(exported_vars)
         append output {<!-- Exported form vars END -->}
     }