diff --git a/sys/src/cmd/nusb/disk/disk.c b/sys/src/cmd/nusb/disk/disk.c
index 60052922b..0bffaa0ba 100644
--- a/sys/src/cmd/nusb/disk/disk.c
+++ b/sys/src/cmd/nusb/disk/disk.c
@@ -812,7 +812,7 @@ dwrite(Req *req)
 		}
 		switch(lun->phase){
 		case Pcmd:
-			if(count != 6 && count != 10){
+			if(count != 6 && count != 10 && count != 12 && count != 16){
 				respond(req, "bad command length");
 				break;
 			}
diff --git a/sys/src/cmd/nusb/disk/ums.h b/sys/src/cmd/nusb/disk/ums.h
index 27572a1c9..f8dbfa4fc 100644
--- a/sys/src/cmd/nusb/disk/ums.h
+++ b/sys/src/cmd/nusb/disk/ums.h
@@ -79,7 +79,7 @@ struct Umsc
 	/* partitions */
 	Part part[Maxparts];
 
-	uchar 	rawcmd[10];
+	uchar 	rawcmd[16];
 	uchar	phase;
 	char	*inq;
 	Ums	*ums;