Heh -- used the right format for a refcount, but forgot
to stop truncating it.
diff --git a/Objects/object.c b/Objects/object.c
index e598b69..3404c35 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -141,7 +141,7 @@
 	PyOS_snprintf(buf, sizeof(buf),
 		      "%s:%i object at %p has negative ref count "
 		      "%" PY_FORMAT_SIZE_T "d",
-		      fname, lineno, op, (long)op->ob_refcnt);
+		      fname, lineno, op, op->ob_refcnt);
 	Py_FatalError(buf);
 }