Transfer Function block in Simulink for variable size input

Dear Tech Support,

The error occurs at the Simulink transfer function block.

My error message roughly:

Simulink cannot propagate the variable-size mode from the output port 1 of the (previous block) to the input port 1 of transfer function".

What can be done in order to make the transfer function block comply with a variable size input ?

The input of the transfer function block is a signal, represented by a (1 x 500) vector.

Thank you in advance !

Sincerely,

Miklos