Function in the library warning CCS.

Hi. I have this warning:

- #169-D argument of type "volatile unsigned char *" is incompatible with parameter of type
     "unsigned char *"

The code works but  I'd like to understand what's the problem . This is part of the code :

I have this array in the main, and I use it as argument of a function on a separate library, where I fill this array :

MAIN :

volatile unsigned char IMEI[15];

Read_IMEI(IMEI);

LIBRARY :

//Read IMEI
//Retrurn 1 if the IMEI have sense. Also fill the IMEI array
unsigned int Read_IMEI(unsigned char array[])
{
    unsigned int ret=1;
    unsigned int z = 0;
    unsigned int x = 0;
    unsigned int y = 0;
    unsigned int i = 0;
    unsigned int j = 0;

    Send_data_UARTA1(command_GSN,8);
    //Wait 500 ms and check the response
    __delay_cycles(8000000);


     y=Counter_UART_A1-23;
     i=Counter_UART_A1-4;
     j=Counter_UART_A1-3;


     if(Counter_UART_A1>23)
     {
         //Response is OK
         if(String_UART_A1[i]=='O' && String_UART_A1[j]=='K')
         {
             //Check if the IMEI have sense
            for(z=y,x=0 ; z<=y+14; z++,x++)
            {
                if((String_UART_A1[z] -'0')>=0 && (String_UART_A1[z]-'0')<=9)
                 {
                     array[x]=String_UART_A1[z];

                 }
                 else
                 {
                     ret= 0;
                 }

            }

            //Check the part of the iMEI with the Producer CODE
            for(x=0 ; x<6; x++)
            {


                if(array[x]!=IMEI_PRODUCER_PART[x])
                {
                    ret = 0;
                }
            }

         }
         else
         {
            ret=0;
         }
     }
     else
     {
        ret=0;
     }


     //CLEAR INDEX
     Counter_UART_A1=0;


return ret;
}

Thanks

Riccardo