diff --git a/hardware/arduino/avr/cores/arduino/USBCore.cpp b/hardware/arduino/avr/cores/arduino/USBCore.cpp
index 44dce72c4..6c8ae633d 100644
--- a/hardware/arduino/avr/cores/arduino/USBCore.cpp
+++ b/hardware/arduino/avr/cores/arduino/USBCore.cpp
@@ -733,7 +733,7 @@ static inline void USB_ClockEnable()
 ISR(USB_GEN_vect)
 {
 	u8 udint = UDINT;
-	UDINT = UDINT &= ~((1<<EORSTI) | (1<<SOFI)); // clear the IRQ flags for the IRQs which are handled here, except WAKEUPI and SUSPI (see below)
+	UDINT &= ~((1<<EORSTI) | (1<<SOFI)); // clear the IRQ flags for the IRQs which are handled here, except WAKEUPI and SUSPI (see below)
 
 	//	End of Reset
 	if (udint & (1<<EORSTI))