diff --git a/build.sbt b/build.sbt
index e26b46f7..507a1d4b 100644
--- a/build.sbt
+++ b/build.sbt
@@ -103,6 +103,10 @@ val io = (project in file("io"))
           "1.3.0",
           "1.4.0",
           "1.5.0",
+          "1.6.0",
+          "1.7.0",
+          "1.8.0",
+          "1.9.0",
         ) map (version => organization.value %% moduleName.value % version)
     }),
     mimaBinaryIssueFilters ++= Seq(
@@ -130,10 +134,7 @@ val io = (project in file("io"))
       exclude[MissingClassProblem]("sbt.internal.io.JavaMilli$"),
       exclude[MissingClassProblem]("sbt.internal.io.JavaMilli"),
       // These are private classes
-      exclude[MissingClassProblem]("sbt.internal.io.FreeBSD64"),
-      exclude[MissingClassProblem]("sbt.internal.io.FreeBSD64FileStat"),
-      exclude[MissingClassProblem]("sbt.internal.io.FreeBSD64Milli"),
-      exclude[MissingClassProblem]("sbt.internal.io.FreeBSD64Milli$"),
+      exclude[MissingClassProblem]("sbt.internal.io.*"),
       // Replaced non-standard __xstat64() with conformant stat() calls
       exclude[DirectMissingMethodProblem]("sbt.internal.io.Linux32.*"),
       exclude[ReversedMissingMethodProblem]("sbt.internal.io.Linux32.*"),
diff --git a/io/src/main/java/sbt/internal/io/MacJNA.java b/io/src/main/java/sbt/internal/io/MacJNA.java
deleted file mode 100644
index 7ad182b2..00000000
--- a/io/src/main/java/sbt/internal/io/MacJNA.java
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- * sbt IO
- * Copyright Scala Center, Lightbend, and Mark Harrah
- *
- * Licensed under Apache License 2.0
- * SPDX-License-Identifier: Apache-2.0
- *
- * See the NOTICE file distributed with this work for
- * additional information regarding copyright ownership.
- */
-
-package sbt.internal.io;
-
-import com.sun.jna.Structure;
-import java.util.List;
-import java.util.Arrays;
-
-public class MacJNA {
-
-  public static class Attrlist extends Structure {
-    public short bitmapcount;
-    public short reserved;
-    public int commonattr;
-    public int volattr;
-    public int dirattr;
-    public int fileattr;
-    public int forkattr;
-    @Override
-    public List<String> getFieldOrder() {
-      return Arrays.asList(new String[]{
-        "bitmapcount", "reserved", "commonattr",
-        "volattr", "dirattr", "fileattr", "forkattr"
-      });
-    };
-  }
-
-  public static class Timespec extends Structure {
-    public long tv_sec;
-    public long tv_nsec;
-    @Override
-    public List<String> getFieldOrder() {
-      return Arrays.asList(new String[]{
-        "tv_sec", "tv_nsec"
-      });
-    };
-  }
-
-  public static final class TimeBuf extends Structure {
-    public int size;
-    public long tv_sec;
-    public long tv_nsec;
-    @Override
-    public List<String> getFieldOrder() {
-      return Arrays.asList(new String[]{
-        "size", "tv_sec", "tv_nsec"
-      });
-    };
-    public TimeBuf() {
-      setAlignType(Structure.ALIGN_NONE);
-    }
-  }
-}
diff --git a/io/src/main/scala/sbt/internal/io/Milli.scala b/io/src/main/scala/sbt/internal/io/Milli.scala
index ca68c116..bbf13c2b 100644
--- a/io/src/main/scala/sbt/internal/io/Milli.scala
+++ b/io/src/main/scala/sbt/internal/io/Milli.scala
@@ -11,339 +11,15 @@
 
 package sbt.internal.io
 
-import java.io.{ File, FileNotFoundException, IOException }
-import java.nio.{ ByteBuffer, ByteOrder }
-import java.nio.file.Files
-import java.util.Date
-
-import com.sun.jna.platform.win32.Kernel32
-import com.sun.jna.platform.win32.WinBase.{ FILETIME, INVALID_HANDLE_VALUE }
-import com.sun.jna.platform.win32.WinError.{
-  ERROR_ACCESS_DENIED,
-  ERROR_FILE_NOT_FOUND,
-  ERROR_INVALID_NAME,
-  ERROR_PATH_NOT_FOUND
-}
-import com.sun.jna.platform.win32.WinNT._
-import com.sun.jna.{ FromNativeContext, Library, NativeMapped, Platform, Native => JNANative }
-import sbt.internal.io.MacJNA._
+import java.io.File
 import sbt.io.JavaMilli
 
-import scala.collection.JavaConverters.mapAsJavaMapConverter
-import scala.reflect.{ ClassTag, classTag }
-import scala.util.control.NonFatal
-
-private abstract class Stat[Time_T](size: Int) extends NativeMapped {
-  val buffer = ByteBuffer.allocate(size).order(ByteOrder.nativeOrder())
-
-  def fromNative(nativeValue: Object, context: FromNativeContext): Nothing =
-    throw new UnsupportedOperationException("Not supported.")
-
-  def toNative(): Object = buffer
-  def nativeType(): Class[ByteBuffer] = classOf[ByteBuffer]
-
-  def getModifiedTimeNative: (Time_T, Time_T) // (sec, nsec)
-}
-
-private abstract class StatLong(size: Int, mtimeOffset: Int, mtimensecOffset: Int)
-    extends Stat[Long](size) {
-  def getModifiedTimeNative = (buffer.getLong(mtimeOffset), buffer.getLong(mtimensecOffset))
-}
-private abstract class StatInt(size: Int, mtimeOffset: Int, mtimensecOffset: Int)
-    extends Stat[Int](size) {
-  def getModifiedTimeNative = (buffer.getInt(mtimeOffset), buffer.getInt(mtimensecOffset))
-}
-
 private[sbt] abstract class Milli {
   def getModifiedTime(filePath: String): Long
   def setModifiedTime(filePath: String, mtime: Long): Unit
   def copyModifiedTime(fromFilePath: String, toFilePath: String): Unit
 }
 
-private abstract class MilliNative[Native] extends Milli {
-  def getModifiedTime(filePath: String): Long =
-    fromNative(getModifiedTimeNative(filePath))
-  def setModifiedTime(filePath: String, mtime: Long): Unit =
-    setModifiedTimeNative(filePath, toNative(mtime))
-
-  // If we have more refined native time information, we can use that
-  // information when copying the modified time, rather than using milliseconds
-  override def copyModifiedTime(fromFilePath: String, toFilePath: String): Unit =
-    setModifiedTimeNative(toFilePath, getModifiedTimeNative(fromFilePath))
-
-  protected def getModifiedTimeNative(filePath: String): Native
-  protected def setModifiedTimeNative(filePath: String, mtimeNative: Native): Unit
-  protected def fromNative(mtimeNative: Native): Long // get milliseconds from native time
-  protected def toNative(mtime: Long): Native // convert milliseconds to native time
-}
-
-/**
- * FFI for standard C library.
- */
-private sealed trait PosixBase extends Library {
-
-  /** http://www.cplusplus.com/reference/cstring/strerror/ */
-  def strerror(errnum: Int): String
-}
-
-private abstract class MilliPosixBase[Interface <: PosixBase: ClassTag, Native]
-    extends MilliNative[Native] {
-  private val options = scala.collection.Map[String, Object]().asJava
-  private final val ENOENT = 2
-  protected val libc: Interface =
-    (JNANative.load(
-      Platform.C_LIBRARY_NAME,
-      classTag[Interface].runtimeClass.asInstanceOf[Class[Interface]],
-      options
-    )): Interface
-  protected def checkedIO[T](filePath: String)(f: => Int) = {
-    if (f != 0) {
-      val errno = JNANative.getLastError()
-      val errStr = libc.strerror(JNANative.getLastError())
-      if (errno == ENOENT)
-        throw new FileNotFoundException(errStr + ": " + filePath)
-      else
-        throw new IOException(errStr + ", file: " + filePath)
-    }
-  }
-}
-
-private trait Posix[Time_T] extends PosixBase
-private abstract class PosixMilli[Interface <: Posix[Time_T]: ClassTag, Time_T]
-    extends MilliPosixBase[Interface, (Time_T, Time_T)] {
-  protected def fromLongLong(sec_nsec: (Long, Long)): Long = {
-    val (sec, nsec) = sec_nsec
-    sec * 1000L + (nsec / 1000000L)
-  }
-  protected def toLongLong(mtime: Long): (Long, Long) = {
-    val sec = mtime / 1000L
-    val nsec = (mtime - sec * 1000L) * 1000000L
-    (sec, nsec)
-  }
-}
-
-private abstract class PosixMilliLong[Interface <: Posix[Long]: ClassTag]
-    extends PosixMilli[Interface, Long] {
-  protected def fromNative(sec_nsec: (Long, Long)) = fromLongLong(sec_nsec)
-  protected def toNative(mtime: Long) = toLongLong(mtime)
-}
-private abstract class PosixMilliInt[Interface <: Posix[Int]: ClassTag]
-    extends PosixMilli[Interface, Int] {
-  protected def fromNative(sec_nsec: (Int, Int)) = {
-    val (sec, nsec) = sec_nsec
-    fromLongLong((sec.toLong, nsec.toLong))
-  }
-  protected def toNative(mtime: Long): (Int, Int) = {
-    val (sec, nsec) = toLongLong(mtime)
-    (sec.toInt, nsec.toInt)
-  }
-}
-
-// Cannot use classtag to initialize buffer: JNA needs
-// a nullary constructor. So, extend manually below.
-//
-// Note: technically, tv_nsec is a long, not a time_t.
-// But on Linux32 a long is 4 bytes (like time_t), and on
-// Linux64 a long is 8 bytes (like time_t), so time_t
-// and long have the same size in both cases.
-//
-private abstract class TimeSpec2[Time_T] extends NativeMapped {
-  val buffer: Array[Time_T]
-  def fromNative(nativeValue: Object, context: FromNativeContext): Nothing =
-    throw new UnsupportedOperationException("Not supported.")
-  def toNative(): Object = buffer
-  def nativeType(): Class[Array[Time_T]] = classOf[Array[Time_T]]
-}
-
-private class TimeSpec2Long extends TimeSpec2[Long] {
-  val buffer = new Array[Long](4)
-  def this(sec: Long, nsec: Long, UTIME_OMIT: Long) = {
-    this()
-    buffer(0) = 0L
-    buffer(1) = UTIME_OMIT
-    buffer(2) = sec
-    buffer(3) = nsec
-  }
-}
-
-private class TimeSpec2Int extends TimeSpec2[Int] {
-  val buffer = new Array[Int](4)
-  def this(sec: Int, nsec: Int, UTIME_OMIT: Int) = {
-    this()
-    buffer(0) = 0
-    buffer(1) = UTIME_OMIT
-    buffer(2) = sec
-    buffer(3) = nsec
-  }
-}
-
-private trait Utimensat[Time_T] extends Posix[Time_T] {
-  def utimensat(dirfd: Int, filePath: String, times: TimeSpec2[Time_T], flags: Int): Int
-}
-private trait MilliUtimensat[Time_T] {
-  protected def AT_FDCWD: Int
-  protected def UTIME_OMIT: Time_T
-}
-private abstract class PosixMilliLongUtim[Interface <: Utimensat[Long]: ClassTag]
-    extends PosixMilliLong[Interface]
-    with MilliUtimensat[Long] {
-  protected def setModifiedTimeNative(filePath: String, mtimeNative: (Long, Long)): Unit = {
-    val (sec, nsec) = mtimeNative
-    val times = new TimeSpec2Long(sec, nsec, UTIME_OMIT)
-    checkedIO(filePath) { libc.utimensat(AT_FDCWD, filePath, times, 0) }
-  }
-}
-private abstract class PosixMilliIntUtim[Interface <: Utimensat[Int]: ClassTag]
-    extends PosixMilliInt[Interface]
-    with MilliUtimensat[Int] {
-  protected def setModifiedTimeNative(filePath: String, mtimeNative: (Int, Int)): Unit = {
-    val (sec, nsec) = mtimeNative
-    val times = new TimeSpec2Int(sec, nsec, UTIME_OMIT)
-    checkedIO(filePath) { libc.utimensat(AT_FDCWD, filePath, times, 0) }
-  }
-}
-
-private class Linux64FileStat extends StatLong(144, 88, 96)
-private trait Linux64 extends Library with Utimensat[Long] {
-  def stat(filePath: String, buf: Linux64FileStat): Int
-}
-private object Linux64Milli extends PosixMilliLongUtim[Linux64] {
-  protected final val AT_FDCWD: Int = -100
-  protected final val UTIME_OMIT: Long = (1L << 30) - 2
-  protected def getModifiedTimeNative(filePath: String) = {
-    val stat = new Linux64FileStat
-    checkedIO(filePath) { libc.stat(filePath, stat) }
-    stat.getModifiedTimeNative
-  }
-}
-
-private class Linux32FileStat extends StatInt(88, 64, 68)
-private trait Linux32 extends Library with Utimensat[Int] {
-  def stat(filePath: String, buf: Linux32FileStat): Int
-}
-private object Linux32Milli extends PosixMilliIntUtim[Linux32] {
-  protected final val AT_FDCWD: Int = -100
-  protected final val UTIME_OMIT: Int = ((1 << 30) - 2)
-  protected def getModifiedTimeNative(filePath: String) = {
-    val stat = new Linux32FileStat
-    checkedIO(filePath) { libc.stat(filePath, stat) }
-    stat.getModifiedTimeNative
-  }
-}
-
-private trait Mac extends Library with Posix[Long] {
-  def getattrlist(
-      path: String,
-      attrlist: Attrlist,
-      attrBuf: TimeBuf,
-      attrBufSize: Int,
-      options: Int
-  ): Int
-  def setattrlist(
-      path: String,
-      attrlist: Attrlist,
-      attrBuf: Timespec,
-      attrBufSize: Int,
-      options: Int
-  ): Int
-}
-private object MacMilli extends PosixMilliLong[Mac] {
-  private val attr = new Attrlist
-  attr.bitmapcount = 5 // ATTR_BIT_MAP_COUNT
-  attr.commonattr = 0x00000400 // ATTR_CMN_MODTIME
-
-  protected def getModifiedTimeNative(filePath: String) = {
-    val buf = new TimeBuf
-    checkedIO(filePath) { libc.getattrlist(filePath, attr, buf, 20 /* buf size */, 0) }
-    (buf.tv_sec, buf.tv_nsec)
-  }
-
-  protected def setModifiedTimeNative(filePath: String, mtimeNative: (Long, Long)): Unit = {
-    val buf = new Timespec
-    val (sec, nsec) = mtimeNative
-    buf.tv_sec = sec
-    buf.tv_nsec = nsec
-    checkedIO(filePath) { libc.setattrlist(filePath, attr, buf, 16 /* buf size */, 0) }
-  }
-}
-
-private object WinMilli extends MilliNative[FILETIME] {
-  import Kernel32.INSTANCE._
-
-  private def getHandle(lpFileName: String, dwDesiredAccess: Int, dwShareMode: Int): HANDLE = {
-    // https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file
-    // \\?\ prefix is used to overcome the 260 character limitation.
-    val fileName = "\\\\?\\" + lpFileName
-    val hFile = CreateFile(
-      fileName,
-      dwDesiredAccess,
-      dwShareMode,
-      null,
-      OPEN_EXISTING,
-      FILE_FLAG_BACKUP_SEMANTICS,
-      null
-    )
-    if (hFile == INVALID_HANDLE_VALUE) {
-      val err = GetLastError()
-      if (err == ERROR_FILE_NOT_FOUND || err == ERROR_PATH_NOT_FOUND)
-        throw new FileNotFoundException("Not found: " + lpFileName)
-      else if (err == ERROR_ACCESS_DENIED)
-        throw new FileNotFoundException("Access denied: " + lpFileName)
-      else if (err == ERROR_INVALID_NAME)
-        throw new FileNotFoundException("Invalid path name " + lpFileName)
-      else {
-        throw new IOException(s"CreateFile() failed with error ${GetLastError()}: $fileName")
-      }
-    }
-    hFile
-  }
-
-  protected def getModifiedTimeNative(filePath: String): FILETIME = {
-    val hFile = getHandle(
-      filePath,
-      FILE_READ_ATTRIBUTES,
-      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
-    )
-    val mtime =
-      try {
-        val modifiedTime = new FILETIME.ByReference()
-        if (!GetFileTime(hFile, /*creationTime*/ null, /*accessTime*/ null, modifiedTime))
-          throw new IOException(
-            "GetFileTime() failed with error " + GetLastError() + " for file " + filePath
-          )
-        modifiedTime
-      } finally {
-        if (!CloseHandle(hFile))
-          throw new IOException(
-            "CloseHandle() after GetFileTime() failed with error " + GetLastError() + " for file " + filePath
-          )
-      }
-    mtime
-  }
-
-  protected def setModifiedTimeNative(filePath: String, fileTime: FILETIME): Unit = {
-    val hFile = getHandle(
-      filePath,
-      FILE_WRITE_ATTRIBUTES,
-      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
-    )
-    try {
-      if (SetFileTime(hFile, null, null, fileTime) == 0)
-        throw new IOException(
-          "SetFileTime() failed with error " + GetLastError() + " for file " + filePath
-        )
-    } finally {
-      if (!CloseHandle(hFile))
-        throw new IOException(
-          "CloseHandle() after SetFileTime() failed with error " + GetLastError() + " for file " + filePath
-        )
-    }
-  }
-
-  protected def fromNative(mtimeNative: FILETIME): Long = mtimeNative.toTime
-  protected def toNative(mtime: Long): FILETIME = new FILETIME(new Date(mtime))
-}
-
 // No native time information? Copy just the milliseconds
 private[sbt] abstract class MilliMilliseconds extends Milli {
   def copyModifiedTime(fromFilePath: String, toFilePath: String): Unit =
@@ -351,95 +27,12 @@ private[sbt] abstract class MilliMilliseconds extends Milli {
 }
 
 object Milli {
-  import Platform._
-
-  //
-  // If the property "sbt.io.jdktimestamps" is set to anything other than
-  // "false", disable native millisecond-accurate modification timestamps.
-  // millis were missing until Java 10, see https://bugs.openjdk.java.net/browse/JDK-8177809
-  //
-  private val jdkTimestamps = {
-    System.getProperty("sbt.io.jdktimestamps") match {
-      case null =>
-        System.getProperty("java.specification.version") match {
-          case null => false
-          case sv =>
-            try {
-              sv.split("\\.").last.toInt >= 10
-            } catch { case NonFatal(_) => false }
-        }
-      case p => p.toLowerCase != "false"
-    }
-  }
-
-  val milli: Milli =
-    if (jdkTimestamps || !isIntel)
-      JavaMilli
-    else
-      getOSType match {
-        case LINUX   => if (is64Bit) Linux64Milli else Linux32Milli
-        case MAC     => MacMilli
-        case WINDOWS => WinMilli
-        case _       => JavaMilli
-      }
-
+  val milli: Milli = JavaMilli
   def getModifiedTime(file: File): Long =
     milli.getModifiedTime(file.getPath)
   def setModifiedTime(file: File, mtime: Long): Unit =
     milli.setModifiedTime(file.getPath, mtime)
   def copyModifiedTime(fromFile: File, toFile: File): Unit =
     milli.copyModifiedTime(fromFile.getPath, toFile.getPath)
-
-  // A sanity check should always be performed upon startup, in order to inform the
-  // user if their file system may betray them because of lack of sub-second
-  // resolution, or if their jdk/system do not offer it.
-  // DO NOT use /tmp to perform the check: use the project dir, where the user files are located
-  // Returns: None if millisecond timestamps worked, Some("diagnostic message") otherwise.
-  def getMilliSupportDiagnostic(projectDir: File): Option[String] =
-    if (jdkTimestamps)
-      None
-    else {
-      val file = Files.createTempFile(projectDir.toPath(), "sbt.io.Milli", "test-file").toFile
-      try {
-        val originalTime = getModifiedTime(file)
-        setModifiedTime(file, originalTime - 27)
-        val newTime = getModifiedTime(file)
-        if (newTime + 27 == originalTime)
-          None
-        else
-          Some {
-            (getOSType match {
-              case LINUX | MAC | WINDOWS =>
-                "Your filesystem does not seem to support sub-second file timestamps "
-              case _ =>
-                "Your OS, filesystem, or Java VM, do not seem to support sub-second file timestamps"
-            }) + (getOSType match {
-              case LINUX =>
-                "(ext2/ext3, for instance, have a 1 sec resolution)"
-              case MAC =>
-                "(HFS+ has a 1 sec resolution, but APFS is more precise)"
-              case WINDOWS =>
-                "(FAT32, for instance, has a 1-2 sec resolution but NTFS is more precise)"
-              case _ =>
-                ""
-            }) + ". That may affect sbt's ability to detect rapid file changes."
-          }
-      } finally {
-        if (!file.delete())
-          throw new IOException(
-            "Unexpected: could not delete temporary file: " + file.getAbsolutePath
-          )
-      }
-    }
+  def getMilliSupportDiagnostic(projectDir: File): Option[String] = None
 }
-
-/*
-object MilliDemo extends App {
-  import Milli._
-  getMilliSupportDiagnostic(new File(".")) map println
-  val file = new File("Milli.scala")
-  println(getModifiedTime(file))
-  setModifiedTime(file, getModifiedTime(file)+1)
-  println(getModifiedTime(file))
-}
- */
diff --git a/project/build.properties b/project/build.properties
index 27430827..abbbce5d 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.9.6
+sbt.version=1.9.8