diff --git a/build.mill b/build.mill
index 3cd9d0a3..12c64f07 100644
--- a/build.mill
+++ b/build.mill
@@ -390,7 +390,7 @@ object sjsonnet extends VersionFileModule {
 
     object client extends JavaModule with SjsonnetPublishModule {
       def artifactName = "sjsonnet-server"
-      def javacOptions = super.javacOptions() ++ Seq("--release", "17")
+      def javacOptions = super.javacOptions() ++ Seq("--release", "17", "-Xlint:deprecation", "-Werror")
       object test extends JavaTests with TestModule.Junit4
     }
 
@@ -398,7 +398,7 @@ object sjsonnet extends VersionFileModule {
       def artifactName = "sjsonnet-server"
       def scalaVersion = SjsonnnetJvmModule.this.crossValue
       def moduleDeps = Seq(SjsonnnetJvmModule.this, client)
-      def scalacOptions = super.scalacOptions() ++ Seq("-release", "17")
+      def scalacOptions = super.scalacOptions() ++ Seq("-release", "17", "-deprecation", "-Werror")
       def javacOptions = super.javacOptions() ++ Seq("--release", "17")
 
       override def prependShellScript = mill.util.Jvm.universalScript(
diff --git a/sjsonnet/server/src/sjsonnet/SjsonnetServerMain.scala b/sjsonnet/server/src/sjsonnet/SjsonnetServerMain.scala
index bedb8519..6c3bcf75 100644
--- a/sjsonnet/server/src/sjsonnet/SjsonnetServerMain.scala
+++ b/sjsonnet/server/src/sjsonnet/SjsonnetServerMain.scala
@@ -213,9 +213,6 @@ class Server[T](
     if (!idle) interruptServer()
 
     t.interrupt()
-    // Thread.stop() is removed in Java 25+; try it for older JVMs but ignore failures
-    try t.stop()
-    catch { case NonFatal(_) => }
 
     if (ClientUtil.isWindows) {
       // Closing the socket on Windows can sometimes take a few seconds.