diff --git a/ArbiterCommand.c b/ArbiterCommand.c
index 47a1111..a8d801d 100644
--- a/ArbiterCommand.c
+++ b/ArbiterCommand.c
@@ -240,7 +240,7 @@ static _Noreturn void Serial_ToCanSpontany_Thread(tTaskSerialToCanSpontany *env)
                     if (data.from_uart == FROM_UART) {
                         env->ioUART->transmit(env->ioUART->env, (uint8_t *) "OK\r\n", sizeof("OK\r\n") - 1, 1000);
                     } else {
-                        env->ioUSB->transmit(env->ioUSB->env, (uint8_t *) "OK\r\n", sizeof("OK\r\n"), 1000);
+                        env->ioUSB->transmit(env->ioUSB->env, (uint8_t *) "OK\r\n", sizeof("OK\r\n") - 1, 1000);
                     }
                 } else {
                     if (data.from_uart == FROM_UART) {