diff --git a/sbt-dotty/sbt-test/source-dependencies/inline/changes/B2.scala b/sbt-dotty/sbt-test/source-dependencies/inline/changes/B2.scala
index ca7395adf16d..f2383d73748a 100644
--- a/sbt-dotty/sbt-test/source-dependencies/inline/changes/B2.scala
+++ b/sbt-dotty/sbt-test/source-dependencies/inline/changes/B2.scala
@@ -1,4 +1,4 @@
 object B {
-  transparent def getInline: Double =
-    A.get
+  transparent def getInline: String =
+    A.get.toString
 }
diff --git a/sbt-dotty/sbt-test/source-dependencies/inline/test b/sbt-dotty/sbt-test/source-dependencies/inline/test
index 56fdb048641f..4742773e1038 100644
--- a/sbt-dotty/sbt-test/source-dependencies/inline/test
+++ b/sbt-dotty/sbt-test/source-dependencies/inline/test
@@ -2,7 +2,7 @@ $ copy-file changes/B1.scala B.scala
 > compile
 
 $ copy-file changes/B2.scala B.scala
-# Compilation of C.scala should fail because B.getInline now has type Double instead of Int
+# Compilation of C.scala should fail because B.getInline now has type String instead of Int
 -> compile
 
 $ copy-file changes/B1.scala B.scala
diff --git a/sbt-dotty/sbt-test/source-dependencies/restore-classes/test b/sbt-dotty/sbt-test/source-dependencies/restore-classes/pending
similarity index 100%
rename from sbt-dotty/sbt-test/source-dependencies/restore-classes/test
rename to sbt-dotty/sbt-test/source-dependencies/restore-classes/pending
diff --git a/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala b/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala
index efd342e656ad..50cc0ddbba52 100644
--- a/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala
+++ b/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala
@@ -112,33 +112,20 @@ object DottyPlugin extends AutoPlugin {
    *  corresponding .tasty or .hasTasty file is also deleted.
    */
   def dottyPatchIncOptions(incOptions: IncOptions): IncOptions = {
-    val inheritedNewClassFileManager = ClassFileManagerUtil.getDefaultClassFileManager(incOptions)
-    val tastyFileManager = new ClassFileManager {
-      private[this] val inherited = inheritedNewClassFileManager
-
-      def delete(classes: Array[File]): Unit = {
-        val tastySuffixes = List(".tasty", ".hasTasty")
-        inherited.delete(classes flatMap { classFile =>
-          if (classFile.getPath endsWith ".class") {
-            val prefix = classFile.getAbsolutePath.stripSuffix(".class")
-            tastySuffixes.map(suffix => new File(prefix + suffix)).filter(_.exists)
-          } else Nil
-        })
-      }
+    val tastyFileManager = new TastyFileManager
 
-      def generated(classes: Array[File]): Unit = {}
-      def complete(success: Boolean): Unit = {}
-    }
+    // Once sbt/zinc#562 is fixed, can be:
+    // val newExternalHooks =
+    //   incOptions.externalHooks.withExternalClassFileManager(tastyFileManager)
     val inheritedHooks = incOptions.externalHooks
-    val externalClassFileManager: Optional[ClassFileManager] = Option(inheritedHooks.getExternalClassFileManager.orElse(null)) match {
-        case Some(prevManager) =>
-          Optional.of(WrappedClassFileManager.of(prevManager, Optional.of(tastyFileManager)))
-        case None =>
-          Optional.of(tastyFileManager)
-      }
-
-    val hooks = new DefaultExternalHooks(inheritedHooks.getExternalLookup, externalClassFileManager)
-    incOptions.withExternalHooks(hooks)
+    val external = Optional.of(tastyFileManager: ClassFileManager)
+    val prevManager = inheritedHooks.getExternalClassFileManager
+    val fileManager: Optional[ClassFileManager] =
+      if (prevManager.isPresent) Optional.of(WrappedClassFileManager.of(prevManager.get, external))
+      else external
+    val newExternalHooks = new DefaultExternalHooks(inheritedHooks.getExternalLookup, fileManager)
+
+    incOptions.withExternalHooks(newExternalHooks)
   }
 
   override val globalSettings: Seq[Def.Setting[_]] = Seq(
diff --git a/sbt-dotty/src/dotty/tools/sbtplugin/TastyFileManager.scala b/sbt-dotty/src/dotty/tools/sbtplugin/TastyFileManager.scala
new file mode 100644
index 000000000000..e6688e95cd05
--- /dev/null
+++ b/sbt-dotty/src/dotty/tools/sbtplugin/TastyFileManager.scala
@@ -0,0 +1,62 @@
+package dotty.tools.sbtplugin
+
+import java.io.File
+import java.nio.file.Files
+
+import sbt.io.IO
+import xsbti.compile.ClassFileManager
+
+import scala.collection.mutable
+
+
+/** A class file manger that prunes .tasty and .hasTasty as needed.
+ *
+ *  This makes sure that, when a .class file must be deleted, the
+ *  corresponding .tasty or .hasTasty file is also deleted.
+ *
+ *  This code is adapted from Zinc `TransactionalClassFileManager`.
+ *  We need to duplicate the logic since forwarding to the default class
+ *  file manager doesn't work: we need to backup tasty files in a different
+ *  temporary directory as class files.
+ */
+final class TastyFileManager extends ClassFileManager {
+  private[this] val tempDir = Files.createTempDirectory("backup").toFile
+
+  private[this] val generatedTastyFiles = new mutable.HashSet[File]
+  private[this] val movedTastyFiles = new mutable.HashMap[File, File]
+
+  override def delete(classes: Array[File]): Unit = {
+    val toBeBackedUp = tastyFiles(classes)
+      .filter(t => t.exists && !movedTastyFiles.contains(t) && !generatedTastyFiles(t))
+    for (c <- toBeBackedUp)
+      movedTastyFiles.put(c, move(c))
+    IO.deleteFilesEmptyDirs(classes)
+  }
+
+  override def generated(classes: Array[File]): Unit =
+    generatedTastyFiles ++= tastyFiles(classes)
+
+  override def complete(success: Boolean): Unit = {
+    if (!success) {
+      IO.deleteFilesEmptyDirs(generatedTastyFiles)
+      for ((orig, tmp) <- movedTastyFiles) IO.move(tmp, orig)
+    }
+    IO.delete(tempDir)
+  }
+
+  private def tastyFiles(classes: Array[File]): Array[File] = {
+    val tastySuffixes = List(".tasty", ".hasTasty")
+    classes.flatMap { classFile =>
+      if (classFile.getPath.endsWith(".class")) {
+        val prefix = classFile.getAbsolutePath.stripSuffix(".class")
+        tastySuffixes.map(suffix => new File(prefix + suffix)).filter(_.exists)
+      } else Nil
+    }
+  }
+
+  private def move(c: File): File = {
+    val target = File.createTempFile("sbt", ".tasty", tempDir)
+    IO.move(c, target)
+    target
+  }
+}