Error initializing SparkContext under a Windows SYSTEM user

We use a SparkLauncher class in our application which is running in a WebSphere Application Server (it is started as a service). When we try to submit an application to Spark (running in standalone mode without Hadoop) , we get this error:
ERROR SparkContext: Error initializing SparkContext.
Exception in thread "main" java.io.IOException: failure to login
at org.apache.hadoop.security.UserGroupInformation.loginUserFromSubject(UserGroupInformation.java:824)
at org.apache.hadoop.security.UserGroupInformation.getLoginUser(UserGroupInformation.java:761)
at org.apache.hadoop.security.UserGroupInformation.getCurrentUser(UserGroupInformation.java:634)
at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2828)
at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2818)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2684)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:373)
at org.apache.hadoop.fs.Path.getFileSystem(Path.java:295)
at org.apache.spark.SparkContext.addFile(SparkContext.scala:1452)
at org.apache.spark.SparkContext.addFile(SparkContext.scala:1425)
at org.apache.spark.SparkContext$$anonfun$12.apply(SparkContext.scala:470)
at org.apache.spark.SparkContext$$anonfun$12.apply(SparkContext.scala:470)
at scala.collection.immutable.List.foreach(List.scala:381)
at org.apache.spark.SparkContext.<init>(SparkContext.scala:470)
at org.apache.spark.SparkContext.<init>(SparkContext.scala:117)
at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:53)
at com.ibm.el.expertise.spark.MatrixCompletionRunner.main(MatrixCompletionRunner.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:95)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:56)
at java.lang.reflect.Method.invoke(Method.java:620)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:738)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:187)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:212)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:126)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
Caused by: javax.security.auth.login.LoginException: java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 3
at com.ibm.security.auth.module.Win64System.getCurrent(Native Method)
at com.ibm.security.auth.module.Win64System.<init>(Win64System.java:74)
at com.ibm.security.auth.module.Win64LoginModule.login(Win64LoginModule.java:143)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:95)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:56)
at java.lang.reflect.Method.invoke(Method.java:620)
at javax.security.auth.login.LoginContext.invoke(LoginContext.java:781)
at javax.security.auth.login.LoginContext.access$000(LoginContext.java:215)
at javax.security.auth.login.LoginContext$4.run(LoginContext.java:706)
at javax.security.auth.login.LoginContext$4.run(LoginContext.java:704)
at java.security.AccessController.doPrivileged(AccessController.java:456)
at javax.security.auth.login.LoginContext.invokePriv(LoginContext.java:703)
at javax.security.auth.login.LoginContext.login(LoginContext.java:609)
at org.apache.hadoop.security.UserGroupInformation.loginUserFromSubject(UserGroupInformation.java:799)
at org.apache.hadoop.security.UserGroupInformation.getLoginUser(UserGroupInformation.java:761)
at org.apache.hadoop.security.UserGroupInformation.getCurrentUser(UserGroupInformation.java:634)
at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2828)
at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2818)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2684)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:373)
at org.apache.hadoop.fs.Path.getFileSystem(Path.java:295)
at org.apache.spark.SparkContext.addFile(SparkContext.scala:1452)
at org.apache.spark.SparkContext.addFile(SparkContext.scala:1425)
at org.apache.spark.SparkContext$$anonfun$12.apply(SparkContext.scala:470)
at org.apache.spark.SparkContext$$anonfun$12.apply(SparkContext.scala:470)
at scala.collection.immutable.List.foreach(List.scala:381)
at org.apache.spark.SparkContext.<init>(SparkContext.scala:470)
at org.apache.spark.SparkContext.<init>(SparkContext.scala:117)
at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:53)
at com.ibm.el.expertise.spark.MatrixCompletionRunner.main(MatrixCompletionRunner.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:95)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:56)
at java.lang.reflect.Method.invoke(Method.java:620)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:738)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:187)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:212)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:126)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)

at javax.security.auth.login.LoginContext.invoke(LoginContext.java:884)
at javax.security.auth.login.LoginContext.access$000(LoginContext.java:215)
at javax.security.auth.login.LoginContext$4.run(LoginContext.java:706)
at javax.security.auth.login.LoginContext$4.run(LoginContext.java:704)
at java.security.AccessController.doPrivileged(AccessController.java:456)
at javax.security.auth.login.LoginContext.invokePriv(LoginContext.java:703)
at javax.security.auth.login.LoginContext.login(LoginContext.java:609)
at org.apache.hadoop.security.UserGroupInformation.loginUserFromSubject(UserGroupInformation.java:799)
... 25 more
17/02/12 19:57:17 INFO ShutdownHookManager: Shutdown hook called
17/02/12 19:57:17 INFO ShutdownHookManager: Deleting directory C:\Windows\Temp\spark-89696e71-a1bd-49f5-86e3-23f2f805f381
getting access token
[getToken] got user access token
getting user info
[getUser] Got TokenUser info
[getUser] userName: SYSTEM, domainName = NT AUTHORITY
[getUser] userSid: S-1-5-18
[getUser] LookupAccountName error: 1332

Spark is using a SYSTEM account for logging even if we specify the environment variable SPARK_USER in a batch file.