diff --git a/compile.c b/compile.c
index d9d072b3a2..8f69a00e80 100644
--- a/compile.c
+++ b/compile.c
@@ -2159,7 +2159,6 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 				rb_bug("iseq_set_sequence: ic_index overflow: index: %d, size: %d", ic_index, body->is_size);
 			    }
 			    generated_iseq[code_index + 1 + j] = (VALUE)ic;
-			    RB_OBJ_WRITTEN(iseq, Qundef, ic);
 			    FL_SET(iseq, ISEQ_MARKABLE_ISEQ);
 			    break;
 			}