After switching to the RedisSessionStateProvider our ASP.NET application started to fail with the following error message:
ERR unknown command 'EVAL'
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: StackExchange.Redis.RedisServerException: ERR unknown command 'EVAL'
A quick check using the INFO command revealed that I was indeed using an older version:
After upgrading to a more recent version, the error went away!