I am getting message “Expected role in mapping” when I start my weblogic server

Hello, I am getting the following error when I try to start my weblogic server.

Unable to deploy EJB: TxNAdminBean from txnadminj2eeservice.jar:

Expected role in mapping

. weblogic.application.ModuleException: Exception preparing module: EJBModule(txnadminj2eeservice.jar)

Unable to deploy EJB: TxNAdminBean from txnadminj2eeservice.jar:

Expected role in mapping

    at weblogic.ejb.container.deployer.EJBModule.prepare(EJBModule.java:469)
    at weblogic.application.internal.flow.ModuleListenerInvoker.prepare(ModuleListenerInvoker.java:199)
    at weblogic.application.internal.flow.DeploymentCallbackFlow$1.next(DeploymentCallbackFlow.java:517)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.DeploymentCallbackFlow.prepare(DeploymentCallbackFlow.java:159)
    Truncated. see log file for complete stacktrace
Caused By: java.lang.AssertionError: Expected role in mapping at weblogic.ejb.container.internal.RuntimeHelper.getRunAsPrincipalFromRoleMapping(RuntimeHelper.java:294) at weblogic.ejb.container.deployer.BeanInfoImpl.calculateRunAsPrincipal(BeanInfoImpl.java:1017) at weblogic.ejb.container.deployer.BeanInfoImpl.prepare(BeanInfoImpl.java:971) at weblogic.ejb.container.deployer.ClientDrivenBeanInfoImpl.prepare(ClientDrivenBeanInfoImpl.java:992) at weblogic.ejb.container.deployer.Ejb3SessionBeanInfoImpl.prepare(Ejb3SessionBeanInfoImpl.java:293) Truncated. see log file for complete stacktrace

I have created a security realm with a group and user. I have created a role too, but not sure why I am still getting the above error. My weblogic-ejb-jar.xml has below -

    <security-role-assignment>
       <role-name>my_role</role-name>
       <principal-name>my_group</principal-name>
     </security-role-assignment>

     <run-as-role-assignment>
       <role-name>my_role</role-name>
       <run-as-principal-name>my_user</run-as-principal-name>
     </run-as-role-assignment>
Am I missing something? Please help me.