diff --git a/akkeeper/src/main/scala/akkeeper/launcher/LaunchArguments.scala b/akkeeper/src/main/scala/akkeeper/launcher/LaunchArguments.scala
index 9d783f4..0e8b406 100644
--- a/akkeeper/src/main/scala/akkeeper/launcher/LaunchArguments.scala
+++ b/akkeeper/src/main/scala/akkeeper/launcher/LaunchArguments.scala
@@ -20,16 +20,16 @@ import java.net.URI
 import com.typesafe.config.Config
 import LaunchArguments._
 
-private[akkeeper] case class LaunchArguments(akkeeperJarPath: URI = new URI("."),
-                                             userJar: URI = new URI("."),
-                                             otherJars: Seq[URI] = Seq.empty,
-                                             resources: Seq[URI] = Seq.empty,
-                                             masterJvmArgs: Seq[String] = Seq.empty,
-                                             userConfig: Option[Config] = None,
-                                             pollInterval: Long = DefaultPollInterval,
-                                             yarnQueue: Option[String] = None,
-                                             principal: Option[String] = None,
-                                             keytab: URI = new URI("."))
+final case class LaunchArguments(akkeeperJarPath: URI = new URI("."),
+                                 userJar: URI = new URI("."),
+                                 otherJars: Seq[URI] = Seq.empty,
+                                 resources: Seq[URI] = Seq.empty,
+                                 masterJvmArgs: Seq[String] = Seq.empty,
+                                 userConfig: Option[Config] = None,
+                                 pollInterval: Long = DefaultPollInterval,
+                                 yarnQueue: Option[String] = None,
+                                 principal: Option[String] = None,
+                                 keytab: Option[URI] = None)
 
 object LaunchArguments {
   val DefaultPollInterval = 1000
diff --git a/akkeeper/src/main/scala/akkeeper/launcher/Launcher.scala b/akkeeper/src/main/scala/akkeeper/launcher/Launcher.scala
index e9b8124..dc91537 100644
--- a/akkeeper/src/main/scala/akkeeper/launcher/Launcher.scala
+++ b/akkeeper/src/main/scala/akkeeper/launcher/Launcher.scala
@@ -23,7 +23,7 @@ import org.apache.hadoop.yarn.conf.YarnConfiguration
 
 import scala.concurrent.{ExecutionContext, Future}
 
-case class LaunchResult(appId: String, masterAddress: Address)
+final case class LaunchResult(appId: String, masterAddress: Address)
 
 /** Launcher for the Akkeeper application. */
 trait Launcher[F[_]] {
diff --git a/akkeeper/src/main/scala/akkeeper/launcher/LauncherMain.scala b/akkeeper/src/main/scala/akkeeper/launcher/LauncherMain.scala
index 68e1ba3..f3c08dd 100644
--- a/akkeeper/src/main/scala/akkeeper/launcher/LauncherMain.scala
+++ b/akkeeper/src/main/scala/akkeeper/launcher/LauncherMain.scala
@@ -76,7 +76,7 @@ object LauncherMain extends App {
     }).text("Principal to be used to login to KDC.")
 
     opt[URI]("keytab").valueName("<keytab path>").action((v, c) => {
-      c.copy(keytab = transformUri(v))
+      c.copy(keytab = Some(transformUri(v)))
     }).text("The full path to the file that contains the keytab for the principal specified above.")
 
     opt[File]("config").valueName("<file>").action((v, c) => {
@@ -96,7 +96,7 @@ object LauncherMain extends App {
       .getOrElse(ConfigFactory.load())
 
     launcherArgs.principal.foreach(p => {
-      YarnUtils.loginFromKeytab(p, launcherArgs.keytab.toString)
+      YarnUtils.loginFromKeytab(p, launcherArgs.keytab.get.toString)
     })
 
     val launcherTimeout =
diff --git a/akkeeper/src/main/scala/akkeeper/launcher/yarn/YarnLauncher.scala b/akkeeper/src/main/scala/akkeeper/launcher/yarn/YarnLauncher.scala
index 374d1ff..936996d 100644
--- a/akkeeper/src/main/scala/akkeeper/launcher/yarn/YarnLauncher.scala
+++ b/akkeeper/src/main/scala/akkeeper/launcher/yarn/YarnLauncher.scala
@@ -120,7 +120,7 @@ final class YarnLauncher(yarnConf: YarnConfiguration,
 
     args.principal.foreach(_ => {
       // Distribute keytab.
-      val keytabResource = resourceManger.createLocalResource(args.keytab.toString,
+      val keytabResource = resourceManger.createLocalResource(args.keytab.get.toString,
         LocalResourceNames.KeytabName)
       localResources.put(LocalResourceNames.KeytabName, keytabResource)
     })
diff --git a/akkeeper/src/test/scala/akkeeper/launcher/yarn/YarnLauncherSpec.scala b/akkeeper/src/test/scala/akkeeper/launcher/yarn/YarnLauncherSpec.scala
index 39026dc..4c656ab 100644
--- a/akkeeper/src/test/scala/akkeeper/launcher/yarn/YarnLauncherSpec.scala
+++ b/akkeeper/src/test/scala/akkeeper/launcher/yarn/YarnLauncherSpec.scala
@@ -91,7 +91,7 @@ class YarnLauncherSpec extends FlatSpec with Matchers with MockFactory
       userConfig = Some(ConfigFactory.load("application-container-test.conf")),
       yarnQueue = Some("queue"),
       principal = Some("username"),
-      keytab = new URI(createResource(resourcesDir, "some.keytab"))
+      keytab = Some(new URI(createResource(resourcesDir, "some.keytab")))
     )
   }