diff --git a/es_print_libusb.c b/es_print_libusb.c
index df69170..9527919 100644
--- a/es_print_libusb.c
+++ b/es_print_libusb.c
@@ -70,7 +70,7 @@
 #define USB_PID_CANON_CP780 780 // XXX
 #define USB_PID_CANON_CP790 790 // XXX
 #define USB_PID_CANON_CP800 0x3214
-#define USB_PID_CANON_CP810 810 // XXX -- completely unknown type
+#define USB_PID_CANON_CP810 0x3256 // XXX -- as of yet unknown file format
 #define USB_PID_CANON_CP900 900 // XXX -- completely unknown type
 
 #define ENDPOINT_UP   0x81