diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index 5bf1fe581..f778dc3e4 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,3 +1,9 @@
+December 18, 2009  (Changes by Graf Zahl)
+- added all known maps requiring inverted sprite sorting to compatibility.txt.
+- added compatibility option to invert sprite sorting. Apparently Doom.exe
+  originally sorted them differently than most source port and on some maps
+  which depends on this it doesn't look right (e.g. Strain MAP13)
+
 December 17, 2009
 - Fixed: Using Transfer_Heights with the SECF_UNDERWATER and
   SECF_FAKEFLOORONLY flags applied the water effect to the ceiling and not
diff --git a/src/compatibility.cpp b/src/compatibility.cpp
index 059a8a4b7..f4fbaa529 100644
--- a/src/compatibility.cpp
+++ b/src/compatibility.cpp
@@ -105,6 +105,7 @@ static FCompatOption Options[] =
 	{ "mbfmonstermove",			COMPATF_MBFMONSTERMOVE, 0 },
 	{ "corpsegibs",				COMPATF_CORPSEGIBS, 0 },
 	{ "noblockfriends",			COMPATF_NOBLOCKFRIENDS, 0 },
+	{ "spritesort",				COMPATF_SPRITESORT, 0 },
 	{ NULL, 0, 0 }
 };
 
diff --git a/src/d_main.cpp b/src/d_main.cpp
index 0aa0b1baf..656875941 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -492,12 +492,12 @@ CUSTOM_CVAR(Int, compatmode, 0, CVAR_ARCHIVE|CVAR_NOINITCALL)
 		break;
 
 	case 1:	// Doom2.exe compatible with a few relaxed settings
-		v = COMPATF_SHORTTEX|COMPATF_STAIRINDEX|COMPATF_USEBLOCKING|COMPATF_NODOORLIGHT|
+		v = COMPATF_SHORTTEX|COMPATF_STAIRINDEX|COMPATF_USEBLOCKING|COMPATF_NODOORLIGHT|COMPATF_SPRITESORT|
 			COMPATF_TRACE|COMPATF_MISSILECLIP|COMPATF_SOUNDTARGET|COMPATF_DEHHEALTH|COMPATF_CROSSDROPOFF;
 		break;
 
 	case 2:	// same as 1 but stricter (NO_PASSMOBJ and INVISIBILITY are also set)
-		v = COMPATF_SHORTTEX|COMPATF_STAIRINDEX|COMPATF_USEBLOCKING|COMPATF_NODOORLIGHT|
+		v = COMPATF_SHORTTEX|COMPATF_STAIRINDEX|COMPATF_USEBLOCKING|COMPATF_NODOORLIGHT|COMPATF_SPRITESORT|
 			COMPATF_TRACE|COMPATF_MISSILECLIP|COMPATF_SOUNDTARGET|COMPATF_NO_PASSMOBJ|COMPATF_LIMITPAIN|
 			COMPATF_DEHHEALTH|COMPATF_INVISIBILITY|COMPATF_CROSSDROPOFF|COMPATF_CORPSEGIBS;
 		break;
@@ -546,6 +546,7 @@ CVAR (Flag, compat_mushroom,	compatflags, COMPATF_MUSHROOM);
 CVAR (Flag, compat_mbfmonstermove,compatflags, COMPATF_MBFMONSTERMOVE);
 CVAR (Flag, compat_corpsegibs,	compatflags, COMPATF_CORPSEGIBS);
 CVAR (Flag, compat_noblockfriends,compatflags,COMPATF_NOBLOCKFRIENDS);
+CVAR (Flag, compat_spritesort,	compatflags,COMPATF_SPRITESORT);
 
 //==========================================================================
 //
diff --git a/src/doomdef.h b/src/doomdef.h
index 868479faa..485f15a5e 100644
--- a/src/doomdef.h
+++ b/src/doomdef.h
@@ -324,6 +324,7 @@ enum
 	COMPATF_MBFMONSTERMOVE	= 1 << 24,	// Monsters are affected by friction and pushers/pullers.
 	COMPATF_CORPSEGIBS		= 1 << 25,	// Crushed monsters are turned into gibs, rather than replaced by gibs.
 	COMPATF_NOBLOCKFRIENDS	= 1 << 26,	// Friendly monsters aren't blocked by monster-blocking lines.
+	COMPATF_SPRITESORT		= 1 << 27,	// Invert sprite sorting order for sprites of equal distance
 };
 
 // Emulate old bugs for select maps. These are not exposed by a cvar
diff --git a/src/g_mapinfo.cpp b/src/g_mapinfo.cpp
index eeb222361..800fa8957 100644
--- a/src/g_mapinfo.cpp
+++ b/src/g_mapinfo.cpp
@@ -1359,6 +1359,7 @@ MapFlagHandlers[] =
 	{ "compat_mbfmonstermove",			MITYPE_COMPATFLAG, COMPATF_MBFMONSTERMOVE},
 	{ "compat_corpsegibs",				MITYPE_COMPATFLAG, COMPATF_CORPSEGIBS},
 	{ "compat_noblockfriends",			MITYPE_COMPATFLAG, COMPATF_NOBLOCKFRIENDS},
+	{ "compat_spritesort",				MITYPE_COMPATFLAG, COMPATF_SPRITESORT},
 	{ "cd_start_track",					MITYPE_EATNEXT,	0, 0 },
 	{ "cd_end1_track",					MITYPE_EATNEXT,	0, 0 },
 	{ "cd_end2_track",					MITYPE_EATNEXT,	0, 0 },
diff --git a/src/m_options.cpp b/src/m_options.cpp
index ac297a2f2..313d0d602 100644
--- a/src/m_options.cpp
+++ b/src/m_options.cpp
@@ -1112,6 +1112,7 @@ static menuitem_t CompatibilityItems[] = {
 	{ bitflag,	"Monster movement is affected by effects",	{&compatflags}, {0}, {0}, {0}, {(value_t *)COMPATF_MBFMONSTERMOVE} },
 	{ bitflag,	"Crushed monsters can be resurrected",		{&compatflags}, {0}, {0}, {0}, {(value_t *)COMPATF_CORPSEGIBS} },
 	{ bitflag,	"Friendly monsters aren't blocked",			{&compatflags}, {0}, {0}, {0}, {(value_t *)COMPATF_NOBLOCKFRIENDS} },
+	{ bitflag,	"Invert sprite sorting",					{&compatflags}, {0}, {0}, {0}, {(value_t *)COMPATF_SPRITESORT} },
 	
 	{ discrete, "Interpolate monster movement",	{&nomonsterinterpolation},		{2.0}, {0.0},	{0.0}, {NoYes} },
 };
diff --git a/src/r_things.cpp b/src/r_things.cpp
index a3a466b4e..a2f18de5f 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -2047,9 +2047,22 @@ void R_SortVisSprites (bool (*compare)(vissprite_t *, vissprite_t *), size_t fir
 		spritesortersize = MaxVisSprites;
 	}
 
-	for (i = 0, spr = firstvissprite; i < vsprcount; i++, spr++)
+	if (!(i_compatflags & COMPATF_SPRITESORT))
 	{
-		spritesorter[i] = *spr;
+		for (i = 0, spr = firstvissprite; i < vsprcount; i++, spr++)
+		{
+			spritesorter[i] = *spr;
+		}
+	}
+	else
+	{
+		// If the compatibility option is on sprites of equal distance need to
+		// be sorted in inverse order. This is most easily achieved by
+		// filling the sort array backwards before the sort.
+		for (i = 0, spr = firstvissprite + vsprcount-1; i < vsprcount; i++, spr--)
+		{
+			spritesorter[i] = *spr;
+		}
 	}
 
 	std::stable_sort(&spritesorter[0], &spritesorter[vsprcount], compare);
diff --git a/wadsrc/static/compatibility.txt b/wadsrc/static/compatibility.txt
index b2a168ce7..a4fd90659 100644
--- a/wadsrc/static/compatibility.txt
+++ b/wadsrc/static/compatibility.txt
@@ -91,3 +91,35 @@ F84AB4557464A383E93F37CD3A82AC48 // MM2 map03
 	corpsegibs
 	vileghosts
 }
+
+// invert the sorting order of overlapping sprites at the same spot
+551D6B416EB3324790BC0F0F74B49600 // Strain map13
+2F49C29691F8565F0B99B27FCF2627E6 // Astrostein 1 MAP01
+55A741F9C2955C2B06F2387E45ED6C62 // MAP02
+4E7286B735671A942C54FAC6CB52A8C3 // MAP03
+825772094FF3569FC3722145F82F820A // MAP04
+CB6CF6BE0EA4A6AB9830FBB7F9192B80 // MAP05
+AB24CCF84C2FE1A543FE033589BD1FBC // MAP06
+6BE0908B4DAFF53AA0A7493C04A608A4 // MAP07
+305275E5E07755E17AAB064981279295 // MAP08
+A8FBF3600088E79D02283C40D12B7F26 // MAP09
+A8FBF3600088E79D02283C40D12B7F26 // MAP09
+F0C95C76237DF617560577767EC21E1C // MAP10
+2A2AF2CDAB7E7A66D28AFC3AA6243DCC // Astrostein 2 map01
+0667DA831EB293D3387579565C11F0DD // map02
+76DA72420EBE0A53D861373D7123DE33 // map03
+5A4F8186580FFE41BCD80960B7F19CA8 // map04
+E3A1EE2A0A2FB27496074057E3FA82F0 // map05
+1CA60DE4062F41DC1A39396228913882 // map06
+DABC3033A734DEF402A8FEF6C2FEDCC2 // map07
+2E8211EA051EA8C3241859D1854386D6 // map08
+EAD27C506AFC856BE07DDDDED20D7ED0 // map09
+7DA47B044E2D5D17EAE2960BBFAEDE1A // Astrostein 3 map10
+46E0F4529E8E396DEDC8DB83443078A7 // map13
+2742D556921FBE753C16175F0C980091 // map14
+AB1A6C1D3898D4259C0645306939374C // map15
+0599F0D0CC1F41F52B7E8214D0348EEA // map17
+CA267398C9B3A8F79349D3394F8B2106 // map20
+{
+	spritesort
+}