The disclosure relates to a method performed by a wireless device, for receiving system information from a network node of a wireless communication system. The system information is received in a synchronization signal (SS) block of an SS burst set comprising at least one SS block. The system information is multiplexed with information providing a time index indicating which SS block of the SS burst set that is being received. The method comprises receiving the information providing the time index, and receiving the system information, which comprises descrambling the system information using a scrambling sequence generated based on the information providing the time index. The method also comprises determining an accuracy of the information providing the time index, based on an error-detection code related to the received system information. The disclosure also relates to corresponding network node method and apparatus.