diff --git a/src/hardware/zketech-ebd-usb/protocol.c b/src/hardware/zketech-ebd-usb/protocol.c
index 3a7fc546..0c99ea50 100644
--- a/src/hardware/zketech-ebd-usb/protocol.c
+++ b/src/hardware/zketech-ebd-usb/protocol.c
@@ -30,7 +30,7 @@ static void log_buf(const char *message, uint8_t buf[], size_t count)
 
 	buffer[count * 2] = 0;
 
-	sr_dbg("%s: %s [%lu bytes]", message, buffer, count);
+	sr_dbg("%s: %s [%zu bytes]", message, buffer, count);
 }
 
 /* Send a command to the device. */