Index: TODO
===================================================================
diff -u -r3946480dcc906b5004bf18ee49b49054fa400e0d -ra709e3ea0a2913db419352f9b1bbee5aa40917e1
--- TODO	(.../TODO)	(revision 3946480dcc906b5004bf18ee49b49054fa400e0d)
+++ TODO	(.../TODO)	(revision a709e3ea0a2913db419352f9b1bbee5aa40917e1)
@@ -5624,12 +5624,10 @@
   parameters is the same.
 - XOTcl 2.0 keeps implicit substdefaults (backward compatible)
 - fix bug: never try to substdefault, when there is no default given.
+- don't swallow errors triggered from variable write traces in configure
 
-
 ========================================================================
 TODO:
-- check error propagation in trace procs
-
 - maybe use as well "$obj eval $cmd" for valuechangedcmd
   Consequence: commands like the folowings become more complicated
   ::nx Class {
Index: generic/nsf.c
===================================================================
diff -u -rdbe0bb3d2a84a4f0836d45aaacb3d4354d6e8805 -ra709e3ea0a2913db419352f9b1bbee5aa40917e1
--- generic/nsf.c	(.../nsf.c)	(revision dbe0bb3d2a84a4f0836d45aaacb3d4354d6e8805)
+++ generic/nsf.c	(.../nsf.c)	(revision a709e3ea0a2913db419352f9b1bbee5aa40917e1)
@@ -28001,7 +28001,20 @@
           goto configure_exit;
         }
       } else {
-        Tcl_ObjSetVar2(interp, paramPtr->nameObj, NULL, newValue, TCL_LEAVE_ERR_MSG|TCL_PARSE_PART1);
+        Tcl_Obj *resultObj;
+        /*
+         * Plain set of the variable.
+         */
+        resultObj = Tcl_ObjSetVar2(interp, paramPtr->nameObj, NULL, newValue, TCL_LEAVE_ERR_MSG|TCL_PARSE_PART1);
+        if (unlikely(resultObj == NULL)) {
+          /*
+           * When the setting of the variable failed (e.g. caused by variable
+           * traces), report the error back.
+           */
+          result = TCL_ERROR;
+          Nsf_PopFrameObj(interp, framePtr);
+          goto configure_exit;
+        }
       }
     }
   }
@@ -28105,7 +28118,7 @@
     goto cget_exit;
   }
 
-  /*fprintf(stderr, "arg %s found, flags %.8x\n", nameString, paramPtr->flags);*/
+  /*fprintf(stderr, "cget: arg %s found, flags %.8x\n", nameString, paramPtr->flags);*/
 
   /*
    * Check for slot invocation