diff --git a/language-server/test/dotty/tools/languageserver/util/server/TestFile.scala b/language-server/test/dotty/tools/languageserver/util/server/TestFile.scala
index a77e82dbdc40..0f3fa36e9900 100644
--- a/language-server/test/dotty/tools/languageserver/util/server/TestFile.scala
+++ b/language-server/test/dotty/tools/languageserver/util/server/TestFile.scala
@@ -5,7 +5,7 @@ import java.nio.file.{Path, Paths}
 import org.eclipse.lsp4j.TextDocumentIdentifier
 
 class TestFile(val file: String) extends AnyVal {
-  def uri: String = s"file://${TestFile.sourceDir}/$file"
+  def uri: String = TestFile.sourceDir.resolve(file).toUri.toString
 }
 
 object TestFile {
diff --git a/language-server/test/dotty/tools/languageserver/util/server/TestServer.scala b/language-server/test/dotty/tools/languageserver/util/server/TestServer.scala
index 39c53ccfb0c9..3c439de6044a 100644
--- a/language-server/test/dotty/tools/languageserver/util/server/TestServer.scala
+++ b/language-server/test/dotty/tools/languageserver/util/server/TestServer.scala
@@ -15,7 +15,10 @@ class TestServer(testFolder: Path) {
 
   private[this] def init(): InitializeResult = {
     // Fill the configuration with values populated by sbt
-    def showSeq[T](lst: Seq[T]): String = lst.map(elem => '"' + elem.toString + '"').mkString("[ ", ", ", " ]")
+    def showSeq[T](lst: Seq[T]): String =
+      lst
+        .map(elem => '"' + elem.toString.replace('\\', '/') + '"')
+        .mkString("[ ", ", ", " ]")
     val dottyIdeJson: String =
       s"""[ {
          |  "id" : "dotty-ide-test",
@@ -23,7 +26,7 @@ class TestServer(testFolder: Path) {
          |  "compilerArguments" : ${showSeq(BuildInfo.ideTestsCompilerArguments)},
          |  "sourceDirectories" : ${showSeq(BuildInfo.ideTestsSourceDirectories)},
          |  "dependencyClasspath" : ${showSeq(BuildInfo.ideTestsDependencyClasspath)},
-         |  "classDirectory" : "${BuildInfo.ideTestsClassDirectory}"
+         |  "classDirectory" : "${BuildInfo.ideTestsClassDirectory.toString.replace('\\','/')}"
          |}
          |]""".stripMargin
     val configFile = testFolder.resolve(DottyLanguageServer.IDE_CONFIG_FILE)