The invention relates to a method for detecting that an additional serving cell is activated is provided. The method is implemented by a wireless device and a network node of a system supporting carrier aggregation. The network node serves the wireless device configured with a first serving cell and the additional serving cell. The network node method comprises configuring (710) the wireless device to transmit feedback information associated with the additional serving cell at a first rate, and transmitting (520) a command to the wireless device to activate the additional serving cell. The method also comprises detecting (530) the activation of the additional serving cell based on reception of feedback information from the wireless device, and configuring (540) the wireless device to transmit feedback information associated with the additional serving cell at a second rate after activation, where the second rate is lower than the first rate.