MongoDB YAML file problems on Windows

Question

I managed to get MongoDB running as a three member replica on Windows 8, but I had problems with configuration files. If I used the new (MongoDB 2.6) file format (YAML) and used the replica set name option as:

replication:
    replSetName: rs1

(or any of the other variants I had tried in YAML format) I would get "Invalid option: replication" error during the installation. When I switched to old conf. file format and used:

replSet=rs1

I had no problems. I am very (very!) new to all this, so I am wondering if I was doing something wrong or is it Mongo 2.6 - Windows problem. Thanks!