Index: generic/tclVar.c
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclVar.c,v
retrieving revision 1.160.2.3
diff -u -r1.160.2.3 tclVar.c
--- generic/tclVar.c	8 Oct 2008 14:52:39 -0000	1.160.2.3
+++ generic/tclVar.c	4 Mar 2009 16:33:03 -0000
@@ -2547,7 +2547,7 @@
 
 	    varValuePtr = TclPtrSetVar(interp, varPtr, arrayPtr, objv[1],
 		    NULL, objv[i], TCL_APPEND_VALUE|TCL_LEAVE_ERR_MSG, -1);
-	    if (varValuePtr == NULL) {
+	    if (varValuePtr == ((Interp *) interp)->emptyObjPtr) {
 		return TCL_ERROR;
 	    }
 	}
