diff --git a/build.sbt b/build.sbt
index 9a98c8f4c..c9fca5ac8 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,7 +4,7 @@ organization := "edu.berkeley.cs"
 name := "chiseltest"
 
 // we keep in sync with chisel version names
-version := "5.0-SNAPSHOT"
+version := "6.0-SNAPSHOT"
 
 scalaVersion := "2.13.10"
 
@@ -50,8 +50,8 @@ publishTo := {
 
 // Provide a managed dependency on X if -DXVersion="" is supplied on the command line.
 val defaultVersions = Map(
-  "chisel3" -> "5.0.0",
-  "firrtl" -> "5.0.0",
+  "chisel3" -> "6.0.0-M2",
+  "firrtl" -> "6.0-SNAPSHOT",
 )
 
 scalacOptions ++= Seq(
@@ -72,7 +72,7 @@ scalacOptions ++= Seq(
 
 libraryDependencies ++= Seq(
   "org.chipsalliance" %% "chisel" % defaultVersions("chisel3"),
-  "edu.berkeley.cs" %% "firrtl" % defaultVersions("firrtl"),
+  "edu.berkeley.cs" %% "firrtl2" % defaultVersions("firrtl"),
   "org.scalatest" %% "scalatest" % "3.2.15",
   "com.lihaoyi" %% "utest" % "0.8.1",
   "net.java.dev.jna" % "jna" % "5.13.0",
diff --git a/src/main/scala/chiseltest/simulator/ChiselBridge.scala b/src/main/scala/chiseltest/simulator/ChiselBridge.scala
index 4f6a88e7c..e6ecad50e 100644
--- a/src/main/scala/chiseltest/simulator/ChiselBridge.scala
+++ b/src/main/scala/chiseltest/simulator/ChiselBridge.scala
@@ -221,13 +221,18 @@ private object ChiselBridge {
     case Connect(info, loc, expr)   => firrtl2.ir.Connect(convert(info), convert(loc), convert(expr))
     case Conditionally(info, pred, conseq, alt) =>
       firrtl2.ir.Conditionally(convert(info), convert(pred), convert(conseq), convert(alt))
-    case EmptyStmt                => firrtl2.ir.EmptyStmt
-    case Block(stmts)             => firrtl2.ir.Block(stmts.map(convert))
-    case DefWire(info, name, tpe) => firrtl2.ir.DefWire(convert(info), name, convert(tpe))
-    case DefRegister(info, name, tpe, clock, reset, init) =>
+    case EmptyStmt                           => firrtl2.ir.EmptyStmt
+    case Block(stmts)                        => firrtl2.ir.Block(stmts.map(convert))
+    case DefWire(info, name, tpe)            => firrtl2.ir.DefWire(convert(info), name, convert(tpe))
+    case DefRegister(info, name, tpe, clock) =>
+      // default is a self reset with a zero reset signal
+      val reset = firrtl2.Utils.zero
+      val firrtl2Tpe = convert(tpe)
+      val init = firrtl2.ir.Reference(name, firrtl2Tpe, firrtl2.RegKind, firrtl2.SourceFlow)
+      firrtl2.ir.DefRegister(convert(info), name, firrtl2Tpe, convert(clock), reset, init)
+    case DefRegisterWithReset(info, name, tpe, clock, reset, init) =>
       firrtl2.ir.DefRegister(convert(info), name, convert(tpe), convert(clock), convert(reset), convert(init))
     case DefInstance(info, name, module, tpe) => firrtl2.ir.DefInstance(convert(info), name, module, convert(tpe))
-    case PartialConnect(info, loc, expr)      => firrtl2.ir.PartialConnect(convert(info), convert(loc), convert(expr))
     case Attach(info, exprs)                  => firrtl2.ir.Attach(convert(info), exprs.map(convert))
     case s: Stop => firrtl2.ir.Stop(convert(s.info), s.ret, convert(s.clk), convert(s.en), name = s.name)
     case p: Print =>
diff --git a/src/test/scala/chiseltest/iotesters/VecFillSpec.scala b/src/test/scala/chiseltest/iotesters/VecFillSpec.scala
index 306e03d66..6b67cbb77 100644
--- a/src/test/scala/chiseltest/iotesters/VecFillSpec.scala
+++ b/src/test/scala/chiseltest/iotesters/VecFillSpec.scala
@@ -8,7 +8,7 @@ import chiseltest._
 
 class VF extends Module {
   val io = IO(new Bundle {
-    val addr = Input(UInt(8.W))
+    val addr = Input(UInt(4.W))
     val value = Output(UInt(8.W))
   })
 
diff --git a/src/test/scala/chiseltest/tests/ChiselEnumTest.scala b/src/test/scala/chiseltest/tests/ChiselEnumTest.scala
index 4a60e4a19..d722e6d72 100644
--- a/src/test/scala/chiseltest/tests/ChiselEnumTest.scala
+++ b/src/test/scala/chiseltest/tests/ChiselEnumTest.scala
@@ -36,7 +36,9 @@ class ChiselEnumTest extends AnyFlatSpec with ChiselScalatestTester {
         val in = Input(UInt(2.W))
         val out = Output(EnumExample())
       })
-      io.out := io.in.asTypeOf(chiselTypeOf(io.out))
+      val (value, safe) = EnumExample.safe(io.in)
+      chisel3.assert(safe)
+      io.out := value
     }) { c =>
       c.io.in.poke(0.U)
       c.io.out.expect(EnumExample.e0)