Maximum step size warning in Simulink when i use state-space block

Hallo Everyone when I use state space block in simulink I see this warning:" Using a default value of 0.2 for maximum step size.The simulation step size will be equal to or less than this value.You can disable this diagnostic by setting 'Automatic solver parameter selection' diagnostic to 'none' in the Diagnostics page of the configuration parameters dialog " ,even SISO or other system .but changing to none I see this error:"Error evaluating expression 'none' for 'MaxStep' specified in the Configuration Parameters dialog for block diagram 'tamrin12of7': Undefined function or variable 'none'."what should I do?