diff --git a/compiler/test/dotty/tools/dotc/IdempotencyTests.scala b/compiler/test/dotty/tools/dotc/IdempotencyTests.scala
index 30dbb47475ff..66988a8f2408 100644
--- a/compiler/test/dotty/tools/dotc/IdempotencyTests.scala
+++ b/compiler/test/dotty/tools/dotc/IdempotencyTests.scala
@@ -18,14 +18,18 @@ class IdempotencyTests {
   import IdempotencyTests._
   import CompilationTest.aggregateTests
 
+  // Flaky test on Windows
+  // https://github.com/lampepfl/dotty/issues/11885
+  val filter = FileFilter.exclude("i6507b")
+
   @Category(Array(classOf[SlowTests]))
   @Test def idempotency: Unit = {
     implicit val testGroup: TestGroup = TestGroup("idempotency")
     val opt = defaultOptions
 
     val posIdempotency = aggregateTests(
-      compileFilesInDir("tests/pos", opt)(TestGroup("idempotency/posIdempotency1")),
-      compileFilesInDir("tests/pos", opt)(TestGroup("idempotency/posIdempotency2")),
+      compileFilesInDir("tests/pos", opt, filter)(TestGroup("idempotency/posIdempotency1")),
+      compileFilesInDir("tests/pos", opt, filter)(TestGroup("idempotency/posIdempotency2")),
     )
 
     val orderIdempotency = {
diff --git a/compiler/test/dotty/tools/vulpix/FileFilter.scala b/compiler/test/dotty/tools/vulpix/FileFilter.scala
index 75c17089a4e1..b2aef8af038e 100644
--- a/compiler/test/dotty/tools/vulpix/FileFilter.scala
+++ b/compiler/test/dotty/tools/vulpix/FileFilter.scala
@@ -5,6 +5,10 @@ sealed trait FileFilter {
 }
 
 object FileFilter {
+  def exclude(file: String): FileFilter = exclude(file :: Nil)
+
+  def exclude(file: String, files: String*): FileFilter =
+    exclude(file :: files.toList)
 
   def exclude(files: List[String]): FileFilter = new FileFilter {
     private val blackList = files.toSet
diff --git a/tests/idempotency/IdempotencyCheck.scala b/tests/idempotency/IdempotencyCheck.scala
index 6f9a8de588de..598f68a8b347 100644
--- a/tests/idempotency/IdempotencyCheck.scala
+++ b/tests/idempotency/IdempotencyCheck.scala
@@ -6,14 +6,6 @@ import java.util.stream.Stream as JStream
 import scala.collection.JavaConverters.*
 
 object IdempotencyCheck {
-  val blacklisted = Set(
-    // No fix needed. Bridges on collections in different order. Second one in scala2 order.
-    s"pos{JFile.separator}Map{JFile.separator}scala{JFile.separator}collection{JFile.separator}immutable/Map",
-    s"pos{JFile.separator}Map{JFile.separator}scala{JFile.separator}collection{JFile.separator}immutable{JFile.separator}AbstractMap",
-    s"pos{JFile.separator}t1203a/NodeSeq",
-    s"pos{JFile.separator}i2345{JFile.separator}Whatever"
-  )
-
   def checkIdempotency(dir1: String, dir2: String): Unit = {
     var failed = 0
     var total = 0
@@ -26,14 +18,14 @@ object IdempotencyCheck {
       val bytecodeFiles = {
         def bytecodeFiles(paths: JStream[JPath], dir: String): List[(String, JPath)] = {
           def isBytecode(file: String) = file.endsWith(".class") || file.endsWith(".tasty")
-          def tupleWithName(f: JPath) = (f.toString.substring(dir.length + 1, f.toString.length - 6), f)
+          def tupleWithName(f: JPath) = (f.toString.substring(dir.length, f.toString.length - 6), f)
           paths.iterator.asScala.filter(path => isBytecode(path.toString)).map(tupleWithName).toList
         }
         bytecodeFiles(JFiles.walk(dir1Path), dir1String) ++ bytecodeFiles(JFiles.walk(dir2Path), dir2String)
       }
       val groups = bytecodeFiles.groupBy(_._1).mapValues(_.map(_._2))
 
-      groups.filterNot(x => blacklisted(x._1)).iterator.flatMap { g =>
+      groups.iterator.flatMap { g =>
         def pred(f: JPath, dir: String, isTasty: Boolean) =
           f.toString.contains(dir) && f.toString.endsWith(if (isTasty) ".tasty" else ".class")
         val class1 = g._2.find(f => pred(f, dir1String, isTasty = false))