diff --git a/conf/modules/mavlink.xml b/conf/modules/mavlink.xml
index 0c5ee3dcbe..7a914eec1b 100644
--- a/conf/modules/mavlink.xml
+++ b/conf/modules/mavlink.xml
@@ -20,12 +20,12 @@
       MAVLINK_PORT ?= UART1
       MAVLINK_PORT_UPPER=$(shell echo $(MAVLINK_PORT) | tr a-z A-Z)
       MAVLINK_PORT_LOWER=$(shell echo $(MAVLINK_PORT) | tr A-Z a-z)
-      ifeq ($(MAVLINK_PORT), UsbS)
+      ifneq (,$(findstring usb,$(MAVLINK_PORT_LOWER)))
       ap.CFLAGS += -DUSE_USB_SERIAL
       ap.srcs += $(SRC_ARCH)/usb_ser_hw.c
       ap.CFLAGS += -DMAVLINK_DEV=usb_serial
       else
-      ifeq ($(findstring UDP,$(MAVLINK_PORT)), UDP)
+      ifneq (,$(findstring udp,$(MAVLINK_PORT_LOWER)))
       include $(CFG_SHARED)/udp.makefile
       $(TARGET).CFLAGS += -DMAVLINK_DEV=$(MAVLINK_PORT_LOWER)
       $(TARGET).CFLAGS += -DUSE_$(MAVLINK_PORT_UPPER)