diff --git a/core/hw/pvr/ta_ctx.h b/core/hw/pvr/ta_ctx.h
index 46d6aeeda..cbc7e1f4e 100644
--- a/core/hw/pvr/ta_ctx.h
+++ b/core/hw/pvr/ta_ctx.h
@@ -166,7 +166,7 @@ struct TA_context
 		rend.global_param_mvo.Init(4096,&rend.Overrun);
 		rend.global_param_tr.Init(4096,&rend.Overrun);
 
-		rend.modtrig.Init(4096,&rend.Overrun);
+		rend.modtrig.Init(8192,&rend.Overrun);
 		
 		Reset();
 	}
diff --git a/core/nullDC.cpp b/core/nullDC.cpp
index 2c7a4df6a..c62db04e8 100755
--- a/core/nullDC.cpp
+++ b/core/nullDC.cpp
@@ -243,6 +243,7 @@ void LoadSettings()
     settings.aica.NoSound			= cfgLoadInt("config","aica.NoSound",0);
 	settings.rend.UseMipmaps		= cfgLoadInt("config","rend.UseMipmaps",1);
 	settings.rend.WideScreen		= cfgLoadInt("config","rend.WideScreen",0);
+	settings.rend.ModifierVolumes	= cfgLoadInt("config","rend.ModifierVolumes",1);
 	
 	settings.pvr.subdivide_transp	= cfgLoadInt("config","pvr.Subdivide",0);
 	
diff --git a/core/rend/gles/gldraw.cpp b/core/rend/gles/gldraw.cpp
index 51d616b52..ed0ae7a3a 100644
--- a/core/rend/gles/gldraw.cpp
+++ b/core/rend/gles/gldraw.cpp
@@ -856,6 +856,7 @@ void SetMVS_Mode(u32 mv_mode,ISP_Modvol ispc)
 
 		if (mv_mode==1)
 		{
+			// Inclusion volume
 			//res : old : final 
 			//0   : 0      : 00
 			//0   : 1      : 01
@@ -881,21 +882,22 @@ void SetMVS_Mode(u32 mv_mode,ISP_Modvol ispc)
 		}
 		else
 		{
+			// Exclusion volume
 			/*
-				this is bugged. a lot.
 				I've only seen a single game use it, so i guess it doesn't matter ? (Zombie revenge)
 				(actually, i think there was also another, racing game)
 			*/
 
+			// The initial value for exclusion volumes is 1 so we need to invert the result before and'ing.
 			//res : old : final 
 			//0   : 0   : 00
-			//0   : 1   : 00
+			//0   : 1   : 01
 			//1   : 0   : 00
-			//1   : 1   : 01
+			//1   : 1   : 00
 
-			//if (2>st) st=1; else st=0;	//can't be done with a single pass
-			glStencilFunc(GL_GREATER,1,3);
-			glStencilOp(GL_ZERO,GL_KEEP,GL_REPLACE);
+			//if (1 == st) st = 1; else st = 0;
+			glStencilFunc(GL_EQUAL, 1, 3);
+			glStencilOp(GL_ZERO,GL_KEEP,GL_KEEP);
 #ifndef NO_STENCIL_WORKAROUND
 			//Look @ comment above -- this looks like a driver bug
 			glStencilOp(GL_ZERO,GL_KEEP,GL_REPLACE);
@@ -986,7 +988,7 @@ void DrawModVols()
 		*/
 
 		glColorMask(GL_FALSE,GL_FALSE,GL_FALSE,GL_FALSE);
-		glDepthFunc(GL_GREATER);
+
 		if ( 0 /* || GetAsyncKeyState(VK_F6)*/ )
 		{
 			//simple single level stencil
@@ -1107,7 +1109,8 @@ void DrawStrips()
 	/*if (!GetAsyncKeyState(VK_F1))*/
 	DrawList<ListType_Opaque,false>(pvrrc.global_param_op);
 
-	//DrawModVols();
+	if (settings.rend.ModifierVolumes)
+		DrawModVols();
 
 	//Alpha tested
 	//setup alpha test state
diff --git a/core/rend/gles/gles.cpp b/core/rend/gles/gles.cpp
index bf38af325..ef16af4e9 100755
--- a/core/rend/gles/gles.cpp
+++ b/core/rend/gles/gles.cpp
@@ -1751,6 +1751,7 @@ bool RenderFrame()
 		glClearColor(0,0,0,1.0f);
 
 	glClearDepthf(0.f); glCheck();
+	glStencilMask(0xFF); glCheck();
 	glClear(GL_COLOR_BUFFER_BIT|GL_STENCIL_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); glCheck();
 
 
diff --git a/core/types.h b/core/types.h
index 56fa73cd5..24df94bde 100644
--- a/core/types.h
+++ b/core/types.h
@@ -615,6 +615,7 @@ struct settings_t
 	{
 		bool UseMipmaps;
 		bool WideScreen;
+		bool ModifierVolumes;
 	} rend;
 
 	struct