From 372733da8cac825e3db8cc4135797ff213b784af Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Sat, 7 Dec 2019 14:58:23 +0200
Subject: [PATCH] - handle mirroring in MNTR sprite renaming

https://forum.zdoom.org/viewtopic.php?t=66583
---
 src/gamedata/w_wad.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/gamedata/w_wad.cpp b/src/gamedata/w_wad.cpp
index 5c37a5998..1d3942a10 100644
--- a/src/gamedata/w_wad.cpp
+++ b/src/gamedata/w_wad.cpp
@@ -885,9 +885,12 @@ void FWadCollection::RenameSprites (const TArray<FString> &deletelumps)
 			{
 				if (LumpInfo[i].lump->dwName == MAKE_ID('M', 'N', 'T', 'R'))
 				{
-					if (LumpInfo[i].lump->Name[4] >= 'F' && LumpInfo[i].lump->Name[4] <= 'K')
+					for (size_t fi : {4, 6})
 					{
-						LumpInfo[i].lump->Name[4] += 'U' - 'F';
+						if (LumpInfo[i].lump->Name[fi] >= 'F' && LumpInfo[i].lump->Name[fi] <= 'K')
+						{
+							LumpInfo[i].lump->Name[fi] += 'U' - 'F';
+						}
 					}
 				}
 			}