diff --git a/build.sc b/build.sc
index 0ff09b4..1d16c17 100644
--- a/build.sc
+++ b/build.sc
@@ -1,30 +1,31 @@
 // build.sc for mill
 import java.io.File
 
-import scala.reflect.internal.util.ScalaClassLoader.URLClassLoader
-
 import mill._
 import mill.scalalib._
 import mill.scalalib.publish._
-import $ivy.`de.tototec::de.tobiasroeser.mill.osgi:0.0.6`
+import $ivy.`de.tototec::de.tobiasroeser.mill.osgi_mill0.9:0.3.2`
+import coursier.Repository
 import de.tobiasroeser.mill.osgi._
+import mill.define.{Target, Task}
 import mill.modules.Jvm
 import os.Path
 
 object Deps {
-
   val asciiDoclet = ivy"org.asciidoctor:asciidoclet:1.5.4"
   val testng = ivy"org.testng:testng:6.11"
   val junit = ivy"junit:junit:4.12"
   val slf4j = ivy"org.slf4j:slf4j-api:1.7.25"
   val logbackClassic = ivy"ch.qos.logback:logback-classic:1.2.3"
   val java17Signature = ivy"org.codehaus.mojo.signature:java17:1.0"
-  val millTestng = ivy"com.lihaoyi:mill-contrib-testng:${sys.props("MILL_VERSION")}"
+  val millTestng = ivy"com.lihaoyi:mill-contrib-testng_2.13:${sys.props("MILL_VERSION")}"
 }
 
 // TODO cross compile with retrolambda
 object lambdatest extends MavenModule with PublishModule with OsgiBundleModule {
 
+  override def osgiBuildMode: OsgiBundleModule.BuildMode = OsgiBundleModule.BuildMode.CalculateManifest
+
   override def millSourcePath: Path = super.millSourcePath / os.up
 
   override def publishVersion = "0.6.3-SNAPSHOT"
@@ -59,29 +60,11 @@ object lambdatest extends MavenModule with PublishModule with OsgiBundleModule {
     )}
   }
 
-  object java7 extends RetrolambdaModule {
+  object retro extends Cross[RetroCross]("7", "6")
+  class RetroCross(version: String) extends RetrolambdaModule {
+    override def bytecodeVersion: T[String] = version
     def baseModule: JavaModule = lambdatest
-    override def retrolambdaVersion = T{ "2.5.6" }
-    def compile: T[PathRef] = T{
-      val dest = T.ctx().dest
-      retrolambdaWorker().retrolambda(
-        inputDir = baseModule.compile().classes.path,
-        outputDir = dest,
-        classpath = baseModule.compileClasspath().toSeq.map(_.path),
-        bytecodeVersion = "7"
-      )
-      PathRef(dest)
-    }
-    override def repositories = baseModule.repositories
-    def localClasspath = T{
-      baseModule.resources() ++ Agg(compile())
-    }
-    def jar: T[PathRef] = T{
-      Jvm.createJar(
-        localClasspath().map(_.path).filter(os.exists),
-        baseModule.manifest()
-      )
-  }
+    override def retrolambdaVersion = T{ "2.5.7" }
   }
 
 }
@@ -91,10 +74,37 @@ trait RetrolambdaWorker {
 }
 
 trait RetrolambdaModule extends CoursierModule {
+  def bytecodeVersion: T[String]
+  def baseModule: JavaModule
+  def compile: T[PathRef] = T{
+    val dest = T.dest
+    retrolambdaWorker().retrolambda(
+      inputDir = baseModule.compile().classes.path,
+      outputDir = dest,
+      classpath = baseModule.compileClasspath().iterator.to(Seq).map(_.path),
+      bytecodeVersion = bytecodeVersion()
+    )
+    PathRef(dest)
+  }
+
+  override def repositoriesTask: Task[Seq[Repository]] = T.task { baseModule.repositoriesTask() }
+
+  def localClasspath: Target[Seq[PathRef]] = T{
+    baseModule.resources() ++ Agg(compile())
+  }
+
+  def jar: T[PathRef] = T{
+    Jvm.createJar(
+      localClasspath().map(_.path).filter(os.exists),
+      baseModule.manifest()
+    )
+  }
+  def manifest: Target[Jvm.JarManifest] = T { baseModule.manifest() }
+
   def retrolambdaVersion: T[String]
   def retrolambdaIvyDeps: T[Agg[Dep]] = T{ Agg(ivy"net.orfjackal.retrolambda:retrolambda:${retrolambdaVersion()}".exclude("*" -> "*")) }
   def retrolambdaClasspath: T[Seq[PathRef]] = T{
-    resolveDeps(retrolambdaIvyDeps)().toSeq
+    resolveDeps(retrolambdaIvyDeps)().iterator.to(Seq)
   }
   def retrolambdaWorker = T.worker {
 //    val cl = new URLClassLoader(retrolambdaClasspath().map(_.path.toNIO.toUri().toURL()));
@@ -110,6 +120,7 @@ trait RetrolambdaModule extends CoursierModule {
             s"-Dretrolambda.inputDir=${inputDir.toIO.getPath()}",
             s"-Dretrolambda.outputDir=${outputDir.toIO.getPath()}",
             s"-Dretrolambda.classpath=${(Seq(inputDir) ++ classpath).map(_.toIO.getPath).mkString(File.pathSeparator)}",
+            s"-Dretrolambda.bytecodeVersion=${bytecodeVersion}",
             s"-javaagent:${retrolambdaClasspath().head.path.toIO.getPath()}"
           ),
           workingDir = outputDir