diff --git a/main/src/main/scala/sbt/Keys.scala b/main/src/main/scala/sbt/Keys.scala
index 4885dea22..8ce837d93 100644
--- a/main/src/main/scala/sbt/Keys.scala
+++ b/main/src/main/scala/sbt/Keys.scala
@@ -27,7 +27,7 @@ import sbt.internal.io.WatchState
 import sbt.internal.librarymanagement.{ CompatibilityWarningOptions, IvySbt }
 import sbt.internal.remotecache.RemoteCacheArtifact
 import sbt.internal.server.ServerHandler
-import sbt.internal.util.{ Appender, AttributeKey, ProgressState, SourcePosition }
+import sbt.internal.util.{ AttributeKey, ProgressState, SourcePosition }
 import sbt.io._
 import sbt.librarymanagement.Configurations.CompilerPlugin
 import sbt.librarymanagement.LibraryManagementCodec._
@@ -61,7 +61,7 @@ object Keys {
   val timingFormat = settingKey[java.text.DateFormat]("The format used for displaying the completion time.").withRank(CSetting)
   @deprecated("", "1.4.0")
   val extraLoggers = settingKey[ScopedKey[_] => Seq[XAppender]]("A function that provides additional loggers for a given setting.").withRank(DSetting)
-  val extraAppenders = settingKey[ScopedKey[_] => Seq[Appender]]("A function that provides additional loggers for a given setting.").withRank(DSetting)
+  val extraAppenders = settingKey[AppenderSupplier]("A function that provides additional loggers for a given setting.").withRank(DSetting)
   val useLog4J = settingKey[Boolean]("Toggles whether or not to use log4j for sbt internal loggers.").withRank(Invisible)
   val logManager = settingKey[LogManager]("The log manager, which creates Loggers for different contexts.").withRank(DSetting)
   private[sbt] val loggerContext = AttributeKey[LoggerContext]("sbt-logger-context", "The logger config which creates Loggers for different contexts.", Int.MaxValue)
diff --git a/main/src/main/scala/sbt/internal/LogManager.scala b/main/src/main/scala/sbt/internal/LogManager.scala
index 99722dbf6..315989bfa 100644
--- a/main/src/main/scala/sbt/internal/LogManager.scala
+++ b/main/src/main/scala/sbt/internal/LogManager.scala
@@ -16,6 +16,7 @@ import sbt.Scope.GlobalScope
 import sbt.internal.util.MainAppender._
 import sbt.internal.util._
 import sbt.util.{ Level, LogExchange, Logger, LoggerContext }
+import org.apache.logging.log4j.core.{ Appender => XAppender }
 
 sealed abstract class LogManager {
   def apply(
@@ -44,6 +45,14 @@ sealed abstract class LogManager {
     backgroundLog(data, state, task, LoggerContext.globalContext)
 }
 
+/**
+ * A functional interface that allows us to preserve binary compatibility
+ * for LogManager.defaults with the old log4j variant.
+ */
+trait AppenderSupplier {
+  def apply(s: ScopedKey[_]): Seq[Appender]
+}
+
 object LogManager {
   import java.util.concurrent.atomic.AtomicInteger
   private val generateId: AtomicInteger = new AtomicInteger
@@ -75,8 +84,14 @@ object LogManager {
   def defaultManager(console: ConsoleOut): LogManager =
     withLoggers((_, _) => defaultScreen(console))
 
+  @deprecated(
+    "use defaults that takes AppenderSupplier instead of ScopedKey[_] => Seq[Appender]",
+    "1.4.0"
+  )
+  def defaults(extra: ScopedKey[_] => Seq[XAppender], console: ConsoleOut): LogManager =
+    defaults((sk: ScopedKey[_]) => extra(sk).map(new ConsoleAppenderFromLog4J("extra", _)), console)
   // This is called by Defaults.
-  def defaults(extra: ScopedKey[_] => Seq[Appender], console: ConsoleOut): LogManager =
+  def defaults(extra: AppenderSupplier, console: ConsoleOut): LogManager =
     withLoggers(
       (task, state) => defaultScreen(console, suppressedMessage(task, state)),
       extra = extra
@@ -89,14 +104,14 @@ object LogManager {
       screen: (ScopedKey[_], State) => Appender = (_, s) => defaultScreen(s.globalLogging.console),
       backed: PrintWriter => Appender = defaultBacked,
       relay: Unit => Appender = defaultRelay,
-      extra: ScopedKey[_] => Seq[Appender] = _ => Nil
+      extra: AppenderSupplier = _ => Nil
   ): LogManager = new DefaultLogManager(screen, backed, relay, extra)
 
   private class DefaultLogManager(
       screen: (ScopedKey[_], State) => Appender,
       backed: PrintWriter => Appender,
       relay: Unit => Appender,
-      extra: ScopedKey[_] => Seq[Appender]
+      extra: AppenderSupplier
   ) extends LogManager {
     def apply(
         data: Settings[Scope],