diff --git a/apps/usb_power_delivery/test.c b/apps/usb_power_delivery/test.c
index 1fb651d..bd67c19 100644
--- a/apps/usb_power_delivery/test.c
+++ b/apps/usb_power_delivery/test.c
@@ -39,7 +39,7 @@ int main(void) {
         uint8_t sop[4];
         fusb_read_fifo(&fusb, 1,  &sop);
 
-        if (sop[0] == 0xe0) {
+        if (sop[0] == FUSB_PACKET_START_MARKER) {
             fusb_read_fifo(&fusb, 2, &sop);
             usb_pd_parse_header(&usbpd, sop);
             for (uint16_t i = 0; i < usbpd.number_of_data_objects; i++) {
diff --git a/lib/fusb/fusb.h b/lib/fusb/fusb.h
index 5404b32..7ba06ba 100644
--- a/lib/fusb/fusb.h
+++ b/lib/fusb/fusb.h
@@ -10,6 +10,8 @@
 #include "pico/stdlib.h"
 #include "hardware/i2c.h"
 
+#define FUSB_PACKET_START_MARKER 0xe0
+
 typedef struct {
     int addr;
     int rate;