Index: openacs-4/packages/xowiki/tcl/form-field-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/form-field-procs.tcl,v
diff -u -r1.284.2.113 -r1.284.2.114
--- openacs-4/packages/xowiki/tcl/form-field-procs.tcl	26 Aug 2020 18:34:59 -0000	1.284.2.113
+++ openacs-4/packages/xowiki/tcl/form-field-procs.tcl	1 Sep 2020 17:20:33 -0000	1.284.2.114
@@ -1670,7 +1670,9 @@
   } {
 
     set content_type_registered [::xo::dc get_value check_content_type {
-      select exists(select 1 from cr_mime_types where mime_type = :content_type)
+      select case when exists
+      (select 1 from cr_mime_types where mime_type = :content_type) then 1 else 0 end
+      from dual
     }]
     #
     # If the provided mime type is not registered, or unknown, try