diff --git a/compile.c b/compile.c
index 4fa3e473e2..5b5d645c07 100644
--- a/compile.c
+++ b/compile.c
@@ -8929,7 +8929,7 @@ ibf_dump_iseq_each(struct ibf_dump *dump, const rb_iseq_t *iseq)
     dump_body.ci_entries =           ibf_dump_ci_entries(dump, iseq);
     dump_body.cc_entries =           NULL;
     dump_body.variable.coverage      = Qnil;
-    dump_body.variable.original_iseq = Qnil;
+    dump_body.variable.original_iseq = NULL;
 
     IBF_W_ALIGN(struct rb_iseq_constant_body);
     return IBF_WV(dump_body);
diff --git a/iseq.c b/iseq.c
index 74a29a6b85..67a89e1a6b 100644
--- a/iseq.c
+++ b/iseq.c
@@ -222,7 +222,6 @@ rb_iseq_mark(const rb_iseq_t *iseq)
 	}
 
 	rb_gc_mark(body->variable.coverage);
-	rb_gc_mark(body->variable.original_iseq);
 	rb_gc_mark(body->location.label);
 	rb_gc_mark(body->location.base_label);
 	rb_gc_mark(body->location.pathobj);
diff --git a/iseq.h b/iseq.h
index de8beff1ad..6789635de3 100644
--- a/iseq.h
+++ b/iseq.h
@@ -46,23 +46,24 @@ ISEQ_FLIP_CNT_INCREMENT(const rb_iseq_t *iseq)
 static inline VALUE *
 ISEQ_ORIGINAL_ISEQ(const rb_iseq_t *iseq)
 {
-    VALUE str = iseq->body->variable.original_iseq;
-    if (RTEST(str)) return (VALUE *)RSTRING_PTR(str);
-    return NULL;
+    return iseq->body->variable.original_iseq;
 }
 
 static inline void
 ISEQ_ORIGINAL_ISEQ_CLEAR(const rb_iseq_t *iseq)
 {
-    RB_OBJ_WRITE(iseq, &iseq->body->variable.original_iseq, Qnil);
+    void *ptr = iseq->body->variable.original_iseq;
+    iseq->body->variable.original_iseq = NULL;
+    if (ptr) {
+        ruby_xfree(ptr);
+    }
 }
 
 static inline VALUE *
 ISEQ_ORIGINAL_ISEQ_ALLOC(const rb_iseq_t *iseq, long size)
 {
-    VALUE str = rb_str_tmp_new(size * sizeof(VALUE));
-    RB_OBJ_WRITE(iseq, &iseq->body->variable.original_iseq, str);
-    return (VALUE *)RSTRING_PTR(str);
+    return iseq->body->variable.original_iseq =
+        ruby_xmalloc2(sizeof(VALUE), size);
 }
 
 #define ISEQ_TRACE_EVENTS (RUBY_EVENT_LINE  | \
diff --git a/vm_core.h b/vm_core.h
index a5ba1900c1..06bd93d885 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -420,7 +420,7 @@ struct rb_iseq_constant_body {
     struct {
 	rb_snum_t flip_count;
 	VALUE coverage;
-	VALUE original_iseq;
+	VALUE *original_iseq;
     } variable;
 
     unsigned int local_table_size;