diff --git a/STM32F4/boards.txt b/STM32F4/boards.txt
index c6841e4..453d520 100644
--- a/STM32F4/boards.txt
+++ b/STM32F4/boards.txt
@@ -79,7 +79,7 @@ netduino2plus.upload.dfuse_addr=0x8000000
 netduino2plus.build.mcu=cortex-m4
 netduino2plus.build.f_cpu=168000000L
 netduino2plus.build.core=maple
-netduino2plus.build.extra_flags=-DMCU_STM32F406VG -mthumb -DSTM32_HIGH_DENSITY -DSTM32F2 -DSTM32F4 -DBOARD_discovery_f4
+netduino2plus.build.extra_flags=-DMCU_STM32F406VG -mthumb -DSTM32_HIGH_DENSITY -DSTM32F2 -DSTM32F4 -DBOARD_discovery_f4 -DARDUINO_STM32F4_NETDUINO2PLUS
 netduino2plus.build.ldscript=ld/jtag.ld
 netduino2plus.build.variant=discovery_f407
 netduino2plus.build.variant_system_lib=lib_f407.a
diff --git a/STM32F4/cores/maple/usb_serial.cpp b/STM32F4/cores/maple/usb_serial.cpp
index d606855..cc726c2 100644
--- a/STM32F4/cores/maple/usb_serial.cpp
+++ b/STM32F4/cores/maple/usb_serial.cpp
@@ -149,7 +149,7 @@ void USBSerial::enableBlockingTx(void) {
 }
 
 void USBSerial::disableBlockingTx(void) {
-	usbEnableBlockingTx();
+	usbDisableBlockingTx();
 }
 
 USBSerial SerialUSB;