Index: openacs-4/packages/acs-tcl/tcl/object-type-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/object-type-procs.tcl,v
diff -u -N -r1.15 -r1.15.2.1
--- openacs-4/packages/acs-tcl/tcl/object-type-procs.tcl	15 Jun 2018 08:39:48 -0000	1.15
+++ openacs-4/packages/acs-tcl/tcl/object-type-procs.tcl	8 Aug 2022 11:01:07 -0000	1.15.2.1
@@ -120,9 +120,12 @@
     if {$no_cache_p} {
         return [db_list supertypes {}]
     } else {
-        return [util_memoize [list acs_object_type::supertypes \
-            -subtype $subtype \
-            -no_cache]]
+        return [acs::per_thread_cache eval \
+                    -key acs-tcl.acs_object_type.supertypes($subtype) {
+                        util_memoize [list acs_object_type::supertypes \
+                                          -subtype $subtype \
+                                          -no_cache]
+                    }]
     }
 }