diff --git a/compiler/src/dotty/tools/backend/jvm/AsmUtils.scala b/compiler/src/dotty/tools/backend/jvm/AsmUtils.scala
index 47d5c1e41361..7f5887d99a7f 100644
--- a/compiler/src/dotty/tools/backend/jvm/AsmUtils.scala
+++ b/compiler/src/dotty/tools/backend/jvm/AsmUtils.scala
@@ -2,7 +2,7 @@ package dotty.tools
 package backend
 package jvm
 
-import scala.tools.asm.tree.{AbstractInsnNode, ClassNode, MethodNode}
+import scala.tools.asm.tree.{AbstractInsnNode}
 import java.io.PrintWriter
 import scala.tools.asm.util.{TraceClassVisitor, TraceMethodVisitor, Textifier}
 import scala.tools.asm.ClassReader
@@ -31,7 +31,7 @@ object AsmUtils {
   final val traceSerializedClassEnabled = false
   final val traceSerializedClassPattern = ""
 
-  def traceMethod(mnode: MethodNode): Unit = {
+  def traceMethod(mnode: MethodNode1): Unit = {
     println(s"Bytecode for method ${mnode.name}")
     val p = new Textifier
     val tracer = new TraceMethodVisitor(p)
@@ -41,7 +41,7 @@ object AsmUtils {
     w.flush()
   }
 
-  def traceClass(cnode: ClassNode): Unit = {
+  def traceClass(cnode: ClassNode1): Unit = {
     println(s"Bytecode for class ${cnode.name}")
     val w = new PrintWriter(System.out)
     cnode.accept(new TraceClassVisitor(w))
@@ -50,8 +50,8 @@ object AsmUtils {
 
   def traceClass(bytes: Array[Byte]): Unit = traceClass(readClass(bytes))
 
-  def readClass(bytes: Array[Byte]): ClassNode = {
-    val node = new ClassNode()
+  def readClass(bytes: Array[Byte]): ClassNode1 = {
+    val node = new ClassNode1()
     new ClassReader(bytes).accept(node, 0)
     node
   }
diff --git a/compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala b/compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala
index 32e676098b33..dea4cf7cb69a 100644
--- a/compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala
@@ -3,6 +3,7 @@ package backend
 package jvm
 
 import scala.tools.asm
+import scala.tools.asm.ClassWriter
 import scala.collection.mutable
 import dotty.tools.io.AbstractFile
 
@@ -126,6 +127,20 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
     }
   }
 
+  /*
+   * can-multi-thread
+   */
+  def createJAttribute(name: String, b: Array[Byte], offset: Int, len: Int): asm.Attribute = {
+    new asm.Attribute(name) {
+      override def write(classWriter: ClassWriter, code: Array[Byte],
+        codeLength: Int, maxStack: Int, maxLocals: Int): asm.ByteVector = {
+        val byteVector = new asm.ByteVector(len)
+        byteVector.putByteArray(b, offset, len)
+        byteVector
+      }
+    }
+  }
+
   /*
    * Custom attribute (JVMS 4.7.1) "ScalaSig" used as marker only
    * i.e., the pickle is contained in a custom annotation, see:
@@ -151,15 +166,6 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
       vp
     }
 
-    /*
-     * can-multi-thread
-     */
-    def createJAttribute(name: String, b: Array[Byte], offset: Int, len: Int): asm.Attribute = {
-      val dest = new Array[Byte](len)
-      System.arraycopy(b, offset, dest, 0, len)
-      new asm.CustomAttr(name, dest)
-    }
-
     /*
      * can-multi-thread
      */
diff --git a/compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala b/compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala
index c6c6d92fdd9c..691571012ccc 100644
--- a/compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala
@@ -53,7 +53,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
     final val MaximumJvmParameters = 254
 
     // current class
-    var cnode: asm.tree.ClassNode  = null
+    var cnode: ClassNode1          = null
     var thisName: String           = null // the internal name of the class being emitted
 
     var claszSymbol: Symbol        = null
@@ -88,7 +88,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
       isCZStaticModule  = claszSymbol.isStaticModuleClass
       thisName          = internalName(claszSymbol)
 
-      cnode = new asm.tree.ClassNode()
+      cnode = new ClassNode1()
 
       initJClass(cnode)
 
@@ -245,7 +245,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
     } // end of method addClassFields()
 
     // current method
-    var mnode: asm.tree.MethodNode = null
+    var mnode: MethodNode1         = null
     var jMethodName: String        = null
     var isMethSymStaticCtor        = false
     var returnType: BType          = null
@@ -524,7 +524,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
         mdesc,
         jgensig,
         mkArrayS(thrownExceptions)
-      ).asInstanceOf[asm.tree.MethodNode]
+      ).asInstanceOf[MethodNode1]
 
       // TODO param names: (m.params map (p => javaName(p.sym)))
 
diff --git a/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala b/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala
index 8a82b6dcc444..54183186dd2e 100644
--- a/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala
+++ b/compiler/src/dotty/tools/backend/jvm/BytecodeWriters.scala
@@ -84,7 +84,7 @@ trait BytecodeWriters {
     private def emitAsmp(jclassBytes: Array[Byte], asmpFile: dotty.tools.io.File): Unit = {
       val pw = asmpFile.printWriter()
       try {
-        val cnode = new asm.tree.ClassNode()
+        val cnode = new ClassNode1()
         val cr    = new asm.ClassReader(jclassBytes)
         cr.accept(cnode, 0)
         val trace = new scala.tools.asm.util.TraceClassVisitor(new java.io.PrintWriter(new java.io.StringWriter()))
diff --git a/compiler/src/dotty/tools/backend/jvm/ClassNode1.java b/compiler/src/dotty/tools/backend/jvm/ClassNode1.java
new file mode 100644
index 000000000000..c5594ae3dea6
--- /dev/null
+++ b/compiler/src/dotty/tools/backend/jvm/ClassNode1.java
@@ -0,0 +1,39 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package dotty.tools.backend.jvm;
+
+import scala.tools.asm.MethodVisitor;
+import scala.tools.asm.Opcodes;
+import scala.tools.asm.tree.ClassNode;
+import scala.tools.asm.tree.MethodNode;
+
+/**
+ * A subclass of {@link ClassNode} to customize the representation of
+ * label nodes with {@link LabelNode1}.
+ */
+public class ClassNode1 extends ClassNode {
+    public ClassNode1() {
+        this(Opcodes.ASM6);
+    }
+
+    public ClassNode1(int api) {
+        super(api);
+    }
+
+    @Override
+    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+        MethodNode method = new MethodNode1(access, name, descriptor, signature, exceptions);
+        methods.add(method);
+        return method;
+    }
+}
diff --git a/compiler/src/dotty/tools/backend/jvm/GenBCode.scala b/compiler/src/dotty/tools/backend/jvm/GenBCode.scala
index ed0e8b14be79..950478dcaabe 100644
--- a/compiler/src/dotty/tools/backend/jvm/GenBCode.scala
+++ b/compiler/src/dotty/tools/backend/jvm/GenBCode.scala
@@ -7,7 +7,6 @@ import dotty.tools.dotc.core.Phases.Phase
 
 import scala.collection.mutable
 import scala.collection.JavaConverters._
-import scala.tools.asm.CustomAttr
 import dotty.tools.dotc.transform.SymUtils._
 import dotty.tools.dotc.interfaces
 import dotty.tools.dotc.util.SourceFile
@@ -240,7 +239,7 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
                 getFileForClassfile(outF, store.name, ".hasTasty")
                 binary
               }
-            val dataAttr = new CustomAttr(nme.TASTYATTR.mangledString, tasty)
+            val dataAttr = createJAttribute(nme.TASTYATTR.mangledString, tasty, 0, tasty.length)
             store.visitAttribute(dataAttr)
           }
 
diff --git a/compiler/src/dotty/tools/backend/jvm/LabelNode1.java b/compiler/src/dotty/tools/backend/jvm/LabelNode1.java
new file mode 100644
index 000000000000..cf91fe619f5d
--- /dev/null
+++ b/compiler/src/dotty/tools/backend/jvm/LabelNode1.java
@@ -0,0 +1,31 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package dotty.tools.backend.jvm;
+
+import scala.tools.asm.Label;
+import scala.tools.asm.tree.ClassNode;
+import scala.tools.asm.tree.LabelNode;
+
+/**
+ * A subclass of {@link LabelNode} to add user-definable flags.
+ */
+public class LabelNode1 extends LabelNode {
+    public LabelNode1() {
+    }
+
+    public LabelNode1(Label label) {
+        super(label);
+    }
+
+    public int flags;
+}
diff --git a/compiler/src/dotty/tools/backend/jvm/MethodNode1.java b/compiler/src/dotty/tools/backend/jvm/MethodNode1.java
new file mode 100644
index 000000000000..bfa4401830ba
--- /dev/null
+++ b/compiler/src/dotty/tools/backend/jvm/MethodNode1.java
@@ -0,0 +1,47 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package dotty.tools.backend.jvm;
+
+import scala.tools.asm.Label;
+import scala.tools.asm.Opcodes;
+import scala.tools.asm.tree.LabelNode;
+import scala.tools.asm.tree.MethodNode;
+/**
+ * A subclass of {@link MethodNode} to customize the representation of
+ * label nodes with {@link LabelNode1}.
+ */
+public class MethodNode1 extends MethodNode {
+    public MethodNode1(int api, int access, String name, String descriptor, String signature, String[] exceptions) {
+        super(api, access, name, descriptor, signature, exceptions);
+    }
+
+    public MethodNode1(int access, String name, String descriptor, String signature, String[] exceptions) {
+        this(Opcodes.ASM6, access, name, descriptor, signature, exceptions);
+    }
+
+    public MethodNode1(int api) {
+        super(api);
+    }
+
+    public MethodNode1() {
+        this(Opcodes.ASM6);
+    }
+
+    @Override
+    protected LabelNode getLabelNode(Label label) {
+        if (!(label.info instanceof LabelNode)) {
+            label.info = new LabelNode1(label);
+        }
+        return (LabelNode) label.info;
+    }
+}
diff --git a/compiler/test/dotty/tools/vulpix/ParallelTesting.scala b/compiler/test/dotty/tools/vulpix/ParallelTesting.scala
index 49963b836b85..12644be88966 100644
--- a/compiler/test/dotty/tools/vulpix/ParallelTesting.scala
+++ b/compiler/test/dotty/tools/vulpix/ParallelTesting.scala
@@ -324,7 +324,8 @@ trait ParallelTesting extends RunnerOrchestration { self =>
 
     protected def compile(files0: Array[JFile], flags0: TestFlags, suppressErrors: Boolean, targetDir: JFile): TestReporter = {
 
-      val flags = flags0 and ("-d", targetDir.getAbsolutePath)
+      val flags = flags0.and("-d", targetDir.getAbsolutePath)
+        .withClasspath(targetDir.getAbsolutePath)
 
       def flattenFiles(f: JFile): Array[JFile] =
         if (f.isDirectory) f.listFiles.flatMap(flattenFiles)
@@ -336,9 +337,7 @@ trait ParallelTesting extends RunnerOrchestration { self =>
         val fullArgs = Array(
           "javac",
           "-encoding", "UTF-8",
-          "-classpath",
-          s"${Properties.scalaLibrary}${JFile.pathSeparator}${targetDir.getAbsolutePath}"
-        ) ++ flags.all.takeRight(2) ++ fs
+        ) ++ flags.javacFlags ++ fs
 
         val process = Runtime.getRuntime.exec(fullArgs)
         val output = Source.fromInputStream(process.getErrorStream).mkString
@@ -366,7 +365,7 @@ trait ParallelTesting extends RunnerOrchestration { self =>
             }
         }
 
-      val allArgs = flags.withClasspath(targetDir.getAbsolutePath).all
+      val allArgs = flags.all
 
       // Compile with a try to catch any StackTrace generated by the compiler:
       try {
diff --git a/compiler/test/dotty/tools/vulpix/TestFlags.scala b/compiler/test/dotty/tools/vulpix/TestFlags.scala
index ac7770c1a8e2..92bd878264e9 100644
--- a/compiler/test/dotty/tools/vulpix/TestFlags.scala
+++ b/compiler/test/dotty/tools/vulpix/TestFlags.scala
@@ -20,6 +20,14 @@ final case class TestFlags(
     TestFlags(defaultClassPath, s"$runClassPath${JFile.pathSeparator}$classPath", options)
 
   def all: Array[String] = Array("-classpath", defaultClassPath) ++ options
+
+  /** Subset of the flags that should be passed to javac. */
+  def javacFlags: Array[String] = {
+    val flags = all
+    val cp = flags.dropWhile(_ != "-classpath").take(2)
+    val output = flags.dropWhile(_ != "-d").take(2)
+    cp ++ output
+  }
 }
 
 object TestFlags {
diff --git a/project/Build.scala b/project/Build.scala
index 1a1e67ec979f..8bd5da3d28f5 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -481,7 +481,7 @@ object Build {
 
       // get libraries onboard
       libraryDependencies ++= Seq(
-        "org.scala-lang.modules" % "scala-asm" % "6.0.0-scala-1", // used by the backend
+        "org.scala-lang.modules" % "scala-asm" % "7.0.0-scala-1", // used by the backend
         // FIXME: Not needed, but should be on the compiler CP
         ("org.scala-lang.modules" %% "scala-xml" % "1.1.0").withDottyCompat(scalaVersion.value),
         "org.scala-lang" % "scala-library" % scalacVersion % "test",