diff --git a/platformio.ini b/platformio.ini
index c51b239..c188fe5 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -54,6 +54,7 @@ build_flags =
     -D NUM_SCREENS=7
     -D I2C_SDA_PIN=35
     -D I2C_SCK_PIN=36
+    -DARDUINO_USB_CDC_ON_BOOT=1
     -D IS_HW_REV_A
 build_unflags = 
   ${btclock_base.build_unflags}