diff --git a/build.sc b/build.sc
index 3dd2b6a65..86b3d745c 100644
--- a/build.sc
+++ b/build.sc
@@ -2,7 +2,7 @@ import mill._, scalalib._
 import coursier.maven.MavenRepository
 
 object ivys {
-  val scala = "2.12.13"
+  val scala = "2.13.10"
   val chisel3 = ivy"edu.berkeley.cs::chisel3:3.5.6"
   val chisel3Plugin = ivy"edu.berkeley.cs:::chisel3-plugin:3.5.6"
 }
@@ -10,7 +10,7 @@ object ivys {
 trait CommonModule extends ScalaModule {
   override def scalaVersion = ivys.scala
 
-  override def scalacOptions = Seq("-Xsource:2.11")
+  override def scalacOptions = Seq("-Ymacro-annotations")
 }
 
 trait HasChisel3 extends ScalaModule {
@@ -25,7 +25,7 @@ trait HasChisel3 extends ScalaModule {
 
 trait HasChiselTests extends SbtModule {
   object test extends SbtModuleTests with TestModule.ScalaTest {
-    override def ivyDeps = Agg(ivy"edu.berkeley.cs::chisel-iotesters:1.2+")
+    override def ivyDeps = Agg(ivy"edu.berkeley.cs::chiseltest:0.5.4")
   }
 }
 
diff --git a/src/main/scala/nutcore/Decode.scala b/src/main/scala/nutcore/Decode.scala
index abec00abe..7c772c041 100644
--- a/src/main/scala/nutcore/Decode.scala
+++ b/src/main/scala/nutcore/Decode.scala
@@ -1,17 +1,17 @@
 /**************************************************************************************
 * Copyright (c) 2020 Institute of Computing Technology, CAS
 * Copyright (c) 2020 University of Chinese Academy of Sciences
-* 
+*
 * NutShell is licensed under Mulan PSL v2.
-* You can use this software according to the terms and conditions of the Mulan PSL v2. 
+* You can use this software according to the terms and conditions of the Mulan PSL v2.
 * You may obtain a copy of Mulan PSL v2 at:
-*             http://license.coscl.org.cn/MulanPSL2 
-* 
-* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER 
-* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR 
-* FIT FOR A PARTICULAR PURPOSE.  
+*             http://license.coscl.org.cn/MulanPSL2
+*
+* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR
+* FIT FOR A PARTICULAR PURPOSE.
 *
-* See the Mulan PSL v2 for more details.  
+* See the Mulan PSL v2 for more details.
 ***************************************************************************************/
 
 package nutcore
@@ -73,8 +73,8 @@ object Instructions extends HasInstrType with HasNutCoreParameter {
   def NOP = 0x00000013.U
   val DecodeDefault = List(InstrN, FuType.csr, CSROpType.jmp)
   def DecodeTable = RVIInstr.table ++ NutCoreTrap.table ++
-    (if (HasMExtension) RVMInstr.table else Nil) ++
-    (if (HasCExtension) RVCInstr.table else Nil) ++
+    (if (HasMExtension) RVMInstr.table else Array.empty) ++
+    (if (HasCExtension) RVCInstr.table else Array.empty) ++
     Priviledged.table ++
     RVAInstr.table ++
     RVZicsrInstr.table ++ RVZifenceiInstr.table
diff --git a/src/main/scala/nutcore/isa/Priviledged.scala b/src/main/scala/nutcore/isa/Priviledged.scala
index af483ee18..be7fe9d6d 100644
--- a/src/main/scala/nutcore/isa/Priviledged.scala
+++ b/src/main/scala/nutcore/isa/Priviledged.scala
@@ -42,5 +42,5 @@ object Priviledged extends HasInstrType {
     FENCE          -> List(InstrS, FuType.mou, MOUOpType.fence), // nop    InstrS -> !wen
     WFI            -> List(InstrI, FuType.alu, ALUOpType.add) // nop
     // FENCE          -> List(InstrB, FuType.mou, MOUOpType.fencei)
-  ) ++ (if (!Settings.get("MmodeOnly")) table_s else Nil)
+  ) ++ (if (!Settings.get("MmodeOnly")) table_s else Array.empty)
 }
diff --git a/src/main/scala/nutcore/isa/RVI.scala b/src/main/scala/nutcore/isa/RVI.scala
index bdd214b64..4690b230b 100644
--- a/src/main/scala/nutcore/isa/RVI.scala
+++ b/src/main/scala/nutcore/isa/RVI.scala
@@ -167,5 +167,5 @@ object RV64IInstr extends HasInstrType {
 
 object RVIInstr extends HasNutCoreParameter {
   val table = RV32I_ALUInstr.table ++ RV32I_BRUInstr.table ++ RV32I_LSUInstr.table ++
-    (if (XLEN == 64) RV64IInstr.table else Nil)
+    (if (XLEN == 64) RV64IInstr.table else Array.empty)
 }
diff --git a/src/main/scala/nutcore/isa/RVM.scala b/src/main/scala/nutcore/isa/RVM.scala
index 501e242dd..7fe1a2d9c 100644
--- a/src/main/scala/nutcore/isa/RVM.scala
+++ b/src/main/scala/nutcore/isa/RVM.scala
@@ -46,7 +46,7 @@ object RV32MInstr extends HasInstrType with HasNutCoreParameter {
     REM            -> List(InstrR, FuType.mdu, MDUOpType.rem),
     REMU           -> List(InstrR, FuType.mdu, MDUOpType.remu)
   )
-  val table = mulTable ++ (if (HasDiv) divTable else Nil)
+  val table = mulTable ++ (if (HasDiv) divTable else Array.empty)
 }
 
 object RV64MInstr extends HasInstrType with HasNutCoreParameter {
@@ -65,9 +65,9 @@ object RV64MInstr extends HasInstrType with HasNutCoreParameter {
     REMW           -> List(InstrR, FuType.mdu, MDUOpType.remw),
     REMUW          -> List(InstrR, FuType.mdu, MDUOpType.remuw)
   )
-  val table = mulTable ++ (if (HasDiv) divTable else Nil)
+  val table = mulTable ++ (if (HasDiv) divTable else Array.empty)
 }
 
 object RVMInstr extends HasNutCoreParameter {
-  val table = RV32MInstr.table ++ (if (XLEN == 64) RV64MInstr.table else Nil)
+  val table = RV32MInstr.table ++ (if (XLEN == 64) RV64MInstr.table else Array.empty)
 }