diff --git a/freemodbus/modbus/rtu/mbrtu.c b/freemodbus/modbus/rtu/mbrtu.c
index 77a2c2f..963fe7d 100644
--- a/freemodbus/modbus/rtu/mbrtu.c
+++ b/freemodbus/modbus/rtu/mbrtu.c
@@ -137,8 +137,11 @@ eMBRTUStart( void )
      */
     eRcvState = STATE_RX_INIT;
     vMBPortSerialEnable( TRUE, FALSE );
-    vMBPortTimersEnable(  );
-
+#if CONFIG_FMB_TIMER_PORT_ENABLED
+    vMBPortTimersEnable( );
+#else
+    pxMBPortCBTimerExpired();
+#endif
     EXIT_CRITICAL_SECTION(  );
 }