} else if (strncmp(arg, "-mmcu=", 6) == 0) {
                                arg += 6;
 
-                               uint8_t valid_prefix = 0;
-
                                if (strncmp(arg, "at90usb", 7) == 0) {
-                                       valid_prefix = 1;
                                        arg += 7;
                                } else if (strncmp(arg, "atmega", 6) == 0) {
-                                       valid_prefix = 1;
                                        arg += 6;
                                } else {
                                        die("Unknown MCU type\n");