diff --git a/hardware/arduino/sam/cores/arduino/USB/CDC.cpp b/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
index 64271b1f8..3c4f9feaf 100644
--- a/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
+++ b/hardware/arduino/sam/cores/arduino/USB/CDC.cpp
@@ -228,7 +228,6 @@ size_t Serial_::write(uint8_t c)
 
 		if (r > 0)
 		{
-			USBD_Flush(CDC_TX);
 			return r;
 		} else
 		{
diff --git a/hardware/arduino/sam/cores/arduino/USB/USBCore.cpp b/hardware/arduino/sam/cores/arduino/USB/USBCore.cpp
index 3b4a2ced4..61113c20b 100644
--- a/hardware/arduino/sam/cores/arduino/USB/USBCore.cpp
+++ b/hardware/arduino/sam/cores/arduino/USB/USBCore.cpp
@@ -397,6 +397,12 @@ static void USB_ISR(void)
 
 		udd_ack_fifocon(CDC_RX);
 	}
+
+	if (Is_udd_sof())
+	{
+		udd_ack_sof();
+		USBD_Flush(CDC_TX);
+	}
 #endif
 
 	// EP 0 Interrupt
diff --git a/hardware/arduino/sam/system/libsam/source/uotghs_device.c b/hardware/arduino/sam/system/libsam/source/uotghs_device.c
index 23e815ccb..dff259658 100644
--- a/hardware/arduino/sam/system/libsam/source/uotghs_device.c
+++ b/hardware/arduino/sam/system/libsam/source/uotghs_device.c
@@ -115,7 +115,7 @@ void UDD_Attach(void)
 
 	// Enable USB line events
 	udd_enable_reset_interrupt();
-	//udd_enable_sof_interrupt();
+	udd_enable_sof_interrupt();
 
 	cpu_irq_restore(flags);
 }
diff --git a/hardware/arduino/sam/variants/arduino_due_x/libsam_sam3x8e_gcc_rel.a b/hardware/arduino/sam/variants/arduino_due_x/libsam_sam3x8e_gcc_rel.a
index a25e77ed9..8488d4ee5 100644
Binary files a/hardware/arduino/sam/variants/arduino_due_x/libsam_sam3x8e_gcc_rel.a and b/hardware/arduino/sam/variants/arduino_due_x/libsam_sam3x8e_gcc_rel.a differ