Do not clear backtrace in Exception#exception

[Bug #15558]

1 files changed, 2 insertions, 2 deletions

diff --git a/error.c b/error.c
index 290ab7a509..2089c3787e 100644
--- a/error.c
+++ b/error.c
@@ -970,11 +970,11 @@ exc_exception(int argc, VALUE *argv, VALUE self)
 {
     VALUE exc;
 
+    argc = rb_check_arity(argc, 0, 1);
     if (argc == 0) return self;
     if (argc == 1 && self == argv[0]) return self;
     exc = rb_obj_clone(self);
-    exc_initialize(argc, argv, exc);
-
+    rb_ivar_set(exc, id_mesg, argv[0]);
     return exc;
 }