diff --git a/flash.h b/flash.h
index d9b3b7d..dc0daef 100644
--- a/flash.h
+++ b/flash.h
@@ -88,6 +88,7 @@
 	PROGRAMMER_IT87SPI,
 	PROGRAMMER_FT2232SPI,
 	PROGRAMMER_SERPROG,
+	PROGRAMMER_INVALID /* This must always be the last entry. */
 };
 
 extern enum programmer programmer;