diff --git a/eval.c b/eval.c
index c34dd2cdd9..6102cfdc86 100644
--- a/eval.c
+++ b/eval.c
@@ -513,7 +513,7 @@ setup_exception(rb_thread_t *th, int tag, volatile VALUE mesg, VALUE cause)
 
 	PUSH_TAG();
 	if ((status = EXEC_TAG()) == 0) {
-	    RB_GC_GUARD(e) = rb_obj_as_string(e);
+	    e = rb_obj_as_string(e);
 	    if (file && line) {
 		warn_printf("Exception `%s' at %s:%d - %"PRIsVALUE"\n",
 			    rb_obj_classname(th->errinfo), file, line, e);