diff --git a/src/codegen.c b/src/codegen.c
index c8f964f56d..d8c83b92c6 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -639,6 +639,11 @@ lambda_body(codegen_scope *s, node *tree, int blk)
       | ((ra & 1) << 5)
       | (pa & 0x1f);
     genop(s, MKOP_Ax(OP_ENTER, a));
+    if (ra) {
+      size_t ppos = s->irep->plen;
+      s->irep->pool[ppos] = mrb_fixnum_value(0);
+      s->irep->plen++;
+    }
     pos = new_label(s);
     for (i=0; i<oa; i++) {
       new_label(s);
diff --git a/src/vm.c b/src/vm.c
index 390fdddea3..e7a9e86dd1 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -723,6 +723,144 @@ argnum_error(mrb_state *mrb, mrb_int num)
 
 #define CALL_MAXARGS 127
 
+int
+mrb_check_export_reps(mrb_state *mrb, mrb_irep *irep, mrb_int drno, int level)
+{
+  int i;
+  mrb_code *pc;
+  mrb_code ins;
+  for (i = 0; i < irep->rlen; i++) {
+    if (mrb_check_export_reps(mrb, irep->reps[i], drno, level + 1)) {
+      return 1;
+    }
+  }
+
+  for (i = 0, pc = irep->iseq; i < irep->ilen; i++, pc++) {
+    ins = *pc;
+    //disasm_once(mrb, irep, ins);
+    switch(GET_OPCODE(ins)) {
+    case OP_GETUPVAR:
+    case OP_SETUPVAR:
+      if (GETARG_B(ins) == drno && GETARG_C(ins) == level) {
+	return 1;
+      }
+      break;
+
+    default:
+      break;
+    }
+  }
+
+  return 0;
+}
+
+int
+mrb_patch_irep_var2fix(mrb_state *mrb, mrb_irep *irep, mrb_int drno)
+{
+  int i;
+  mrb_code *oiseq = irep->iseq;
+  mrb_code *pc;
+  mrb_code ins;
+  mrb_int tdrno = drno;
+
+  for (i = 0; i < irep->rlen; i++) {
+    if (mrb_check_export_reps(mrb, irep->reps[i], drno, 0)) {
+      return 0;
+    }
+  }
+
+  irep->iseq = (mrb_code*)mrb_malloc(mrb, sizeof(mrb_code)*irep->ilen);
+  for (i = 0, pc = oiseq; i < irep->ilen; i++, pc++) {
+    ins = *pc;
+    irep->iseq[i] = ins;
+
+    if (GET_OPCODE(ins) == OP_ARRAY &&
+	GET_OPCODE(*(pc + 1)) == OP_MOVE &&
+	GETARG_B(*(pc + 1)) == drno &&
+	GET_OPCODE(*(pc + 2)) == OP_ARYCAT &&
+	GET_OPCODE(*(pc + 3)) == OP_SEND &&
+	GETARG_C(*(pc + 3)) == 127) {
+
+      if (GETARG_C(ins) == 0) {
+	irep->iseq[i++] = MKOP_A(OP_NOP, 0);
+	pc++;
+	ins = *pc;
+	irep->iseq[i++] = MKOP_AB(OP_MOVE, GETARG_A(ins) - 1, GETARG_B(ins));
+	pc++;
+	irep->iseq[i++] = MKOP_A(OP_NOP, 0);
+	pc++;
+	ins = *pc;
+	irep->iseq[i] = MKOP_ABC(OP_SEND, GETARG_A(ins), GETARG_B(ins), 1);
+      }
+      else {
+	mrb_free(mrb, irep->iseq);
+	irep->iseq = oiseq;
+	return 0;
+      }
+    }
+
+    if (GET_OPCODE(ins) == OP_MOVE) {
+      if (GETARG_B(ins) == drno) {
+	tdrno = GETARG_A(ins);
+      }
+      else if (GETARG_A(ins) == drno) {
+	mrb_free(mrb, irep->iseq);
+	irep->iseq = oiseq;
+	return 0;
+      }
+    }
+
+    if (GET_OPCODE(ins) == OP_RETURN) {
+      if (   GETARG_A(ins) == tdrno
+	  || GETARG_A(ins) == drno) {
+	mrb_free(mrb, irep->iseq);
+	irep->iseq = oiseq;
+	return 0;
+      }
+    }
+
+    if (GET_OPCODE(ins) == OP_SEND &&
+	(GETARG_A(ins) == tdrno ||
+	 (GETARG_C(ins) == 1 && GETARG_A(ins) + 1 == tdrno))) {
+      if (GETARG_C(ins) == 127) {
+	irep->iseq[i] = MKOP_ABC(OP_SEND, GETARG_A(ins), GETARG_B(ins), 1);
+      }
+      else if (strcmp(mrb_sym2name(mrb, irep->syms[GETARG_B(ins)]), "__svalue") == 0) {
+	irep->iseq[i] = MKOP_A(OP_NOP, 0);
+      }
+      else if (strcmp(mrb_sym2name(mrb, irep->syms[GETARG_B(ins)]), "size") == 0) {
+	irep->iseq[i] = MKOP_AB(OP_LOADI, tdrno, 1);
+      }
+      else if (strcmp(mrb_sym2name(mrb, irep->syms[GETARG_B(ins)]), "[]") == 0) {
+	irep->iseq[i] = MKOP_A(OP_NOP, 0);
+      }
+      else {
+	mrb_free(mrb, irep->iseq);
+	irep->iseq = oiseq;
+	return 0;
+      }
+    }
+    else {
+      switch (GET_OPCODE(ins)) {
+      case OP_SEND:
+      case OP_ARRAY:
+      case OP_HASH:
+      case OP_ADD:
+      case OP_SUB:
+	if (GETARG_A(ins) <= tdrno &&
+	    tdrno <= GETARG_A(ins) + GETARG_C(ins)) {
+	  mrb_free(mrb, irep->iseq);
+	  irep->iseq = oiseq;
+	  return 0;
+	}
+	break;
+      }
+    }
+  }
+
+  return 1;
+}
+
 MRB_API mrb_value
 mrb_context_run(mrb_state *mrb, struct RProc *proc, mrb_value self, unsigned int stack_keep)
 {
@@ -1418,7 +1556,43 @@ mrb_context_run(mrb_state *mrb, struct RProc *proc, mrb_value self, unsigned int
         }
         if (r) {
           rnum = argc-m1-o-m2;
-          regs[m1+o+1] = mrb_ary_new_from_values(mrb, rnum, argv+m1+o);
+	  if (rnum == 1) {
+	    int ipos = 0;
+	    mrb_irep *nirep = (mrb_irep *)mrb_fixnum(irep->pool[ipos]);
+	    struct RProc *p;
+
+	    if (nirep == NULL) {
+	      mrb_irep *cirep = mrb_add_irep(mrb);
+	      *cirep = *irep;
+	      if (mrb_patch_irep_var2fix(mrb, cirep, m1 + o + 1)) {
+		p = mrb_proc_new(mrb, cirep);
+		p->flags = proc->flags;
+		p->body.irep->refcnt++;
+		p->target_class = proc->target_class;
+		p->env = proc->env;
+		irep->pool[ipos] = mrb_fixnum_value((mrb_int)cirep);
+		mrb->c->ci->proc = proc = p;
+		irep = cirep;
+		pc = cirep->iseq;
+	      }
+	      else {
+		regs[m1+o+1] = mrb_ary_new_from_values(mrb, rnum, argv+m1+o);
+	      }
+	    }
+	    else {
+	      p = mrb_proc_new(mrb, nirep);
+	      p->flags = proc->flags;
+	      p->body.irep->refcnt++;
+	      p->target_class = proc->target_class;
+	      p->env = proc->env;
+	      mrb->c->ci->proc = proc = p;
+	      irep = nirep;
+	      pc = nirep->iseq;
+	    }
+	  }
+	  else {
+	    regs[m1+o+1] = mrb_ary_new_from_values(mrb, rnum, argv+m1+o);
+	  }
         }
         if (m2) {
           if (argc-m2 > m1) {