diff --git a/src/doomdef.h b/src/doomdef.h
index bdeb81611f..5d70ecd206 100644
--- a/src/doomdef.h
+++ b/src/doomdef.h
@@ -251,6 +251,7 @@ enum
 	BCOMPATF_NOSLOPEID			= 1 << 9,	// disable line IDs on slopes.
 	BCOMPATF_CLIPMIDTEX			= 1 << 10,	// Always Clip midtex's in the software renderer (required to run certain GZDoom maps, has no effect in the hardware renderer)
 	BCOMPATF_NOSECTIONMERGE		= 1 << 11,	// (for IWAD maps) keep separate sections for sectors with intra-sector linedefs. 
+	BCOMPATF_NOMIRRORS			= 1 << 12,	// disable mirrors, for maps that have broken setups.
 };
 
 // phares 3/20/98:
diff --git a/src/maploader/compatibility.cpp b/src/maploader/compatibility.cpp
index 3549cd0bb4..802ec3465e 100644
--- a/src/maploader/compatibility.cpp
+++ b/src/maploader/compatibility.cpp
@@ -127,6 +127,7 @@ static FCompatOption Options[] =
 	{ "noslopeid",				BCOMPATF_NOSLOPEID, SLOT_BCOMPAT },
 	{ "clipmidtex",				BCOMPATF_CLIPMIDTEX, SLOT_BCOMPAT },
 	{ "nosectionmerge",			BCOMPATF_NOSECTIONMERGE, SLOT_BCOMPAT },
+	{ "nomirrors",				BCOMPATF_NOMIRRORS, SLOT_BCOMPAT },
 
 
 	// list copied from g_mapinfo.cpp
diff --git a/src/rendering/hwrenderer/scene/hw_sky.cpp b/src/rendering/hwrenderer/scene/hw_sky.cpp
index 5e4fc02ef8..0af7309b21 100644
--- a/src/rendering/hwrenderer/scene/hw_sky.cpp
+++ b/src/rendering/hwrenderer/scene/hw_sky.cpp
@@ -155,7 +155,7 @@ void HWWall::SkyPlane(HWDrawInfo *di, sector_t *sector, int plane, bool allowref
 			break;
 		}
 	}
-	else if (allowreflect && sector->GetReflect(plane) > 0)
+	else if (allowreflect && sector->GetReflect(plane) > 0 && !(di->Level->ib_compatflags & BCOMPATF_NOMIRRORS))
 	{
         auto vpz = di->Viewpoint.Pos.Z;
 		if ((plane == sector_t::ceiling && vpz > sector->ceilingplane.fD()) ||
diff --git a/src/rendering/hwrenderer/scene/hw_walls.cpp b/src/rendering/hwrenderer/scene/hw_walls.cpp
index 88ed520687..b049ee172b 100644
--- a/src/rendering/hwrenderer/scene/hw_walls.cpp
+++ b/src/rendering/hwrenderer/scene/hw_walls.cpp
@@ -1273,7 +1273,7 @@ void HWWall::DoTexture(HWDrawInfo *di, int _type,seg_t * seg, int peg,
 	if (!SetWallCoordinates(seg, &tci, floatceilingref, topleft, topright, bottomleft, bottomright, 
 							seg->sidedef->GetTextureXOffset(texpos))) return;
 
-	if (seg->linedef->special == Line_Mirror && _type == RENDERWALL_M1S && gl_mirrors)
+	if (seg->linedef->special == Line_Mirror && _type == RENDERWALL_M1S && gl_mirrors && !(di->Level->ib_compatflags & BCOMPATF_NOMIRRORS))
 	{
 		PutPortal(di, PORTALTYPE_MIRROR, -1);
 	}
diff --git a/wadsrc/static/compatibility.txt b/wadsrc/static/compatibility.txt
index 635e27d70e..d80950583e 100644
--- a/wadsrc/static/compatibility.txt
+++ b/wadsrc/static/compatibility.txt
@@ -320,3 +320,8 @@ F50C91A05E1A1E646690517641F0D1DD // daedalus.wad map19
 {
 	shorttex
 }
+
+65C155579BEA34642A7B83DF5481B29B // Conf256.pk3 CONF55
+{
+	nomirrors
+}