diff --git a/Marlin/pins_TEENSYLU.h b/Marlin/pins_TEENSYLU.h
index 775837767d..2269b31576 100644
--- a/Marlin/pins_TEENSYLU.h
+++ b/Marlin/pins_TEENSYLU.h
@@ -37,6 +37,7 @@
 
 #define BOARD_NAME         "Teensylu"
 
+#define USBCON 1286  // Disable MarlinSerial etc.
 #define LARGE_FLASH        true
 
 #define X_STEP_PIN          0