diff --git a/STM32F4/variants/discovery_f407/variant.h b/STM32F4/variants/discovery_f407/variant.h
index 8a88623..8782ccc 100644
--- a/STM32F4/variants/discovery_f407/variant.h
+++ b/STM32F4/variants/discovery_f407/variant.h
@@ -2,7 +2,7 @@
 #define _VARIANT_ARDUINO_STM32_
 
 #define digitalPinToPort(P)        ( PIN_MAP[P].gpio_device )
-#define digitalPinToBitMask(P)     ( BIT(PIN_MAP[P].gpio_bit) )
+#define digitalPinToBitMask(P)     ( BIT(P&0x0F) )
 #define portOutputRegister(port)   ( &(port->regs->ODR) )
 #define portInputRegister(port)    ( &(port->regs->IDR) )