diff --git a/winusb.c b/winusb.c
index 1ba2f96..1f78f9a 100644
--- a/winusb.c
+++ b/winusb.c
@@ -50,7 +50,7 @@ static struct winusb_compatible_id_descriptor winusb_wcid = {
 };
 
 static const struct usb_string_descriptor winusb_string_descriptor = {
-	.bLength = sizeof(struct usb_string_descriptor) + sizeof(WINUSB_EXTRA_STRING),
+	.bLength = 0x12,
 	.bDescriptorType = USB_DT_STRING,
 	.wData = WINUSB_EXTRA_STRING
 };
diff --git a/winusb.h b/winusb.h
index 1f2ff9a..16a6df1 100644
--- a/winusb.h
+++ b/winusb.h
@@ -23,7 +23,7 @@
 
 // Arbitrary, but must be equivalent to the last character in extra string
 #define WINUSB_MS_VENDOR_CODE '!'
-#define WINUSB_EXTRA_STRING u"MSFT100!"
+#define WINUSB_EXTRA_STRING {'M', 'S', 'F', 'T', '1', '0', '0', WINUSB_MS_VENDOR_CODE}
 
 extern void winusb_setup(usbd_device* usbd_dev, uint8_t interface);