1 files changed, 5 insertions, 1 deletions
diff --git a/Teensy.mk b/Teensy.mk
index dc807a8..8a441e7 100644
--- a/Teensy.mk
+++ b/Teensy.mk
@@ -135,8 +135,12 @@ endif
 
 ########################################################################
 # FLAGS
+ifndef USB_TYPE
+    USB_TYPE = USB_SERIAL
+endif
+
+CPPFLAGS += -DLAYOUT_US_ENGLISH -D$(USB_TYPE)
 
-CPPFLAGS += -DLAYOUT_US_ENGLISH -DUSB_SERIAL
 CPPFLAGS += $(call PARSE_TEENSY,$(BOARD_TAG),build.option)
 
 CXXFLAGS += $(call PARSE_TEENSY,$(BOARD_TAG),build.cppoption)