diff --git a/src/actor.h b/src/actor.h
index 0336c4185..1d1090c19 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -407,12 +407,14 @@ enum ActorRenderFlag
 	RF_SPRITETYPEMASK	= 0x7000,	// ---Different sprite types, not all implemented
 	RF_FACESPRITE		= 0x0000,	// Face sprite
 	RF_WALLSPRITE		= 0x1000,	// Wall sprite
-	RF_FLOORSPRITE		= 0x2000,	// Floor sprite
+	RF_FLATSPRITE		= 0x2000,	// Flat sprite
 	RF_VOXELSPRITE		= 0x3000,	// Voxel object
+	RF_PITCHFLATSPRITE	= 0x4000,	// [MC] Flat sprite that rotates around pitch (GZDoom only)
 	RF_INVISIBLE		= 0x8000,	// Don't bother drawing this actor
 
 	RF_FORCEYBILLBOARD		= 0x10000,	// [BB] OpenGL only: draw with y axis billboard, i.e. anchored to the floor (overrides gl_billboard_mode setting)
 	RF_FORCEXYBILLBOARD		= 0x20000,	// [BB] OpenGL only: draw with xy axis billboard, i.e. unanchored (overrides gl_billboard_mode setting)
+	RF_ROLLSPRITE		= 0x40000,	//[marrub]roll the sprite billboard
 };
 
 // This translucency value produces the closest match to Heretic's TINTTAB.
@@ -974,6 +976,7 @@ public:
 	DVector3		OldRenderPos;
 
 	DRotator		Angles;
+	DAngle			FlatAngle;
 	DVector3		Vel;
 	double			Speed;
 	double			FloatSpeed;
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index b7d887195..77e862028 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -262,7 +262,8 @@ void AActor::Serialize(FArchive &arc)
 		<< projectilepassheight
 		<< Vel
 		<< tics
-		<< state;
+		<< state
+		<< FlatAngle;
 	if (arc.IsStoring())
 	{
 		int dmg;
diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index 34a9cf02c..20848f478 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -6881,3 +6881,25 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_FaceMovementDirection)
 	}
 	ACTION_RETURN_BOOL(true);
 }
+
+//===========================================================================
+//
+// A_SetFlatAngle
+//
+// Set actor's flat angle (in degrees). GZDoom only. Requires the 
+// (PITCH)FLATSPRITE flag to have any visible effect.
+//
+//===========================================================================
+DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_SetFlatAngle)
+{
+	PARAM_ACTION_PROLOGUE;
+	PARAM_FLOAT_OPT(flatangle) { flatangle = 0; }
+	PARAM_INT_OPT(ptr) { ptr = AAPTR_DEFAULT; }
+	
+	AActor *ref = COPY_AAPTR(self, ptr);
+	if (ref != NULL)
+	{
+		ref->FlatAngle = flatangle;
+	}
+	return 0;
+}
\ No newline at end of file
diff --git a/src/thingdef/thingdef_data.cpp b/src/thingdef/thingdef_data.cpp
index efb7be0c2..8b245e828 100644
--- a/src/thingdef/thingdef_data.cpp
+++ b/src/thingdef/thingdef_data.cpp
@@ -265,6 +265,11 @@ static FFlagDef ActorFlagDefs[]=
 	DEFINE_FLAG(RF, INVISIBLE, AActor, renderflags),
 	DEFINE_FLAG(RF, FORCEYBILLBOARD, AActor, renderflags),
 	DEFINE_FLAG(RF, FORCEXYBILLBOARD, AActor, renderflags),
+	DEFINE_FLAG(RF, ROLLSPRITE, AActor, renderflags), // [marrub] roll the sprite billboard 
+			// [fgsfds] Flat sprites
+	DEFINE_FLAG(RF, FLATSPRITE, AActor, renderflags),
+	DEFINE_FLAG(RF, WALLSPRITE, AActor, renderflags),
+	DEFINE_FLAG(RF, PITCHFLATSPRITE, AActor, renderflags),
 
 	// Bounce flags
 	DEFINE_FLAG2(BOUNCE_Walls, BOUNCEONWALLS, AActor, BounceFlags),
diff --git a/src/version.h b/src/version.h
index 21d05b3ed..68c7d0325 100644
--- a/src/version.h
+++ b/src/version.h
@@ -72,11 +72,11 @@ const char *GetVersionString();
 // SAVESIG should match SAVEVER.
 
 // MINSAVEVER is the minimum level snapshot version that can be loaded.
-#define MINSAVEVER	4545
+#define MINSAVEVER	4546
 
 // Use 4500 as the base git save version, since it's higher than the
 // SVN revision ever got.
-#define SAVEVER 4545
+#define SAVEVER 4546
 
 #define SAVEVERSTRINGIFY2(x) #x
 #define SAVEVERSTRINGIFY(x) SAVEVERSTRINGIFY2(x)
diff --git a/wadsrc/static/actors/actor.txt b/wadsrc/static/actors/actor.txt
index 8b35be30d..f47a1d87a 100644
--- a/wadsrc/static/actors/actor.txt
+++ b/wadsrc/static/actors/actor.txt
@@ -325,6 +325,7 @@ ACTOR Actor native //: Thinker
 	native state A_CheckSightOrRange(float distance, state label, bool two_dimension = false);
 	native state A_CheckRange(float distance, state label, bool two_dimension = false);
 	action native bool A_FaceMovementDirection(float offset = 0, float anglelimit = 0, float pitchlimit = 0, int flags = 0, int ptr = AAPTR_DEFAULT);
+	action native A_SetFlatAngle(float flatangle = 0, int ptr = AAPTR_DEFAULT);
 
 	native void A_RearrangePointers(int newtarget, int newmaster = AAPTR_DEFAULT, int newtracer = AAPTR_DEFAULT, int flags=0);
 	native void A_TransferPointer(int ptr_source, int ptr_recepient, int sourcefield, int recepientfield=AAPTR_DEFAULT, int flags=0);