diff --git a/src/drivers/px4io/px4io.cpp b/src/drivers/px4io/px4io.cpp
index 08e697b9f8..ef6ca04e97 100644
--- a/src/drivers/px4io/px4io.cpp
+++ b/src/drivers/px4io/px4io.cpp
@@ -2530,7 +2530,7 @@ px4io_main(int argc, char *argv[])
 		}
 
 		PX4IO_Uploader *up;
-		const char *fn[3];
+		const char *fn[4];
 
 		/* work out what we're uploading... */
 		if (argc > 2) {