diff --git a/Board-STM32F407-Discovery.md b/Board-STM32F407-Discovery.md
index 172b838..d79b724 100644
--- a/Board-STM32F407-Discovery.md
+++ b/Board-STM32F407-Discovery.md
@@ -39,6 +39,7 @@ sudo apt-get install dfu-util
 ```
 # f055:9800 - STM32F4 Discovery running MicroPython in USB Serial Mode (CN5)
 ATTRS{idVendor}=="f055", ENV{ID_MM_DEVICE_IGNORE}="1"
+ATTRS{idVendor}=="f055", ENV{ID_MM_PORT_IGNORE}="1"
 ATTRS{idVendor}=="f055", ENV{MTP_NO_PROBE}="1"
 SUBSYSTEMS=="usb", ATTRS{idVendor}=="f055", MODE:="0666"
 KERNEL=="ttyACM*", ATTRS{idVendor}=="f055", MODE:="0666"