A method (500) for a user terminal (120, 130) in a cellular system (100). The user terminal (120, 130) applies (505) a timing advance to transmissions to a controlling node (140). The user terminal (120, 130) requests (510) communication with the controlling node (140) by a special message (MSG 1), in response to which the user terminal (120, 130) receives (515) a message (MSG 2) which includes an updated value for the timing advance. The user terminal (120, 130) compares (520) the updated value with the value of the timing advance that the user terminal had prior to the reception of said response message. If the difference (Δ) between the prior value and the updated value is greater than a first predetermined threshold (T1) or below a second predetermined threshold (T2), the user terminal (120, 130) ignores (525) the response message (MSG 2) and renews its request for communication.