Index: generic/nsf.c
===================================================================
diff -u -N -r8e7256166e6acd815879baed0d2a95ca0230deae -r63c904a4ea0a45b77f8a2b0a3245424487907479
--- generic/nsf.c	(.../nsf.c)	(revision 8e7256166e6acd815879baed0d2a95ca0230deae)
+++ generic/nsf.c	(.../nsf.c)	(revision 63c904a4ea0a45b77f8a2b0a3245424487907479)
@@ -23374,9 +23374,12 @@
 
 #if defined(NSF_FORWARD_WITH_ONERROR)
   if (unlikely(result == TCL_ERROR && tcd->onerror != NULL)) {
-    fprintf(stderr, "==== DEBUG AppVeyor: calling NsfForwardPrintError with error <<%s>>\n", ObjStr(Tcl_GetObjResult(interp)));
-    result = NsfForwardPrintError(interp, tcd, objc, objv, "%s",
-                                  ObjStr(Tcl_GetObjResult(interp)));
+    Tcl_Obj *resultObj = Tcl_GetObjResult(interp);
+
+    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));
+    DECR_REF_COUNT(resultObj);
   }
 #endif