diff --git a/usr.sbin/bsdinstall/partedit/gpart_ops.c b/usr.sbin/bsdinstall/partedit/gpart_ops.c
index b2cfef597fd6..d6a2c44c4dd4 100644
--- a/usr.sbin/bsdinstall/partedit/gpart_ops.c
+++ b/usr.sbin/bsdinstall/partedit/gpart_ops.c
@@ -856,7 +856,7 @@ gpart_max_free(struct ggeom *geom, intmax_t *npartstart)
 	}
 
 	if (end - lastend > maxsize) {
-		maxsize = end - lastend - 1;
+		maxsize = end - lastend;
 		maxstart = lastend + 1;
 	}