Index: generic/nsf.c
===================================================================
diff -u -N -r63c904a4ea0a45b77f8a2b0a3245424487907479 -r9e6766c4da4c53a9c719d9a66286519e8984c053
--- generic/nsf.c	(.../nsf.c)	(revision 63c904a4ea0a45b77f8a2b0a3245424487907479)
+++ generic/nsf.c	(.../nsf.c)	(revision 9e6766c4da4c53a9c719d9a66286519e8984c053)
@@ -23375,10 +23375,11 @@
 #if defined(NSF_FORWARD_WITH_ONERROR)
   if (unlikely(result == TCL_ERROR && tcd->onerror != NULL)) {
     Tcl_Obj *resultObj = Tcl_GetObjResult(interp);
+    const char *errorMsg =  ObjStr(resultObj);
 
     INCR_REF_COUNT(resultObj);
-    // fprintf(stderr, "==== DEBUG AppVeyor: calling NsfForwardPrintError with error <<%s>>\n", ObjStr(resultObj));
-    result = NsfForwardPrintError(interp, tcd, objc, objv, "%s", ObjStr(resultObj));
+    fprintf(stderr, "==== DEBUG AppVeyor: calling NsfForwardPrintError with <<%s>> (len %lu)\n", errorMsg, strlen(errorMsg));
+    result = NsfForwardPrintError(interp, tcd, objc, objv, "%s", errorMsg);
     DECR_REF_COUNT(resultObj);
   }
 #endif