1 files changed, 8 insertions, 3 deletions
diff --git a/iseq.c b/iseq.c
index f475ca7a37..98eaa03c3a 100644
--- a/iseq.c
+++ b/iseq.c
@@ -660,9 +660,14 @@ insn_operand_intern(rb_iseq_t *iseq,
       case TS_ID:		/* ID (symbol) */
 	op = ID2SYM(op);
       case TS_VALUE:		/* VALUE */
-	ret = rb_inspect(op);
-	if (CLASS_OF(op) == rb_cISeq) {
-	    rb_ary_push(child, op);
+	if (op == Qundef) {
+	    ret = rb_str_new2("undef");
+	}
+	else {
+	    ret = rb_inspect(op);
+	    if (CLASS_OF(op) == rb_cISeq) {
+		rb_ary_push(child, op);
+	    }
 	}
 	break;