diff --git a/README.md b/README.md
index 5254bcab..eab7f74f 100644
--- a/README.md
+++ b/README.md
@@ -166,9 +166,12 @@ any other Steam features.
 The RBDOOM-3-BFG Edition GPL Source Code release includes functionality for rendering Bink Videos through FFmpeg or libbinkdec.
 
 ### Back End Rendering of Stencil Shadows
-The Doom 3 BFG Edition GPL Source Code release does not include functionality enabling rendering
+The RBOOM-3-BFG Edition GPL Source Code release includes functionality enabling rendering
 of stencil shadows via the "depth fail" method, a functionality commonly known as "Carmack's Reverse".
 
+This method was patented by Creative Labs and has finally expired on 2019-10-13.
+(see https://patents.google.com/patent/US6384822B1/en for expiration status)
+
 ---
 ## License <a name="license"></a>
 See docs/COPYING.txt for the GNU GENERAL PUBLIC LICENSE
diff --git a/neo/renderer/OpenGL/RenderBackend_GL.cpp b/neo/renderer/OpenGL/RenderBackend_GL.cpp
index cc7070ce..edd002c8 100644
--- a/neo/renderer/OpenGL/RenderBackend_GL.cpp
+++ b/neo/renderer/OpenGL/RenderBackend_GL.cpp
@@ -1614,7 +1614,9 @@ void idRenderBackend::DrawStencilShadowPass( const drawSurf_t* drawSurf, const b
 	}
 	else
 	{
-		// Z-fail
+		// Z-fail (Carmack's Reverse)
+		glStencilOpSeparate( GL_FRONT, GL_KEEP, GL_DECR, GL_KEEP );
+		glStencilOpSeparate( GL_BACK, GL_KEEP, GL_INCR, GL_KEEP );
 	}
 
 	// get vertex buffer
diff --git a/neo/renderer/RenderBackend.cpp b/neo/renderer/RenderBackend.cpp
index 06251325..3a36d049 100644
--- a/neo/renderer/RenderBackend.cpp
+++ b/neo/renderer/RenderBackend.cpp
@@ -42,7 +42,7 @@ If you have questions concerning this license or the applicable additional terms
 idCVar r_drawEyeColor( "r_drawEyeColor", "0", CVAR_RENDERER | CVAR_BOOL, "Draw a colored box, red = left eye, blue = right eye, grey = non-stereo" );
 idCVar r_motionBlur( "r_motionBlur", "0", CVAR_RENDERER | CVAR_INTEGER | CVAR_ARCHIVE, "1 - 5, log2 of the number of motion blur samples" );
 idCVar r_forceZPassStencilShadows( "r_forceZPassStencilShadows", "0", CVAR_RENDERER | CVAR_BOOL, "force Z-pass rendering for performance testing" );
-idCVar r_useStencilShadowPreload( "r_useStencilShadowPreload", "1", CVAR_RENDERER | CVAR_BOOL, "use stencil shadow preload algorithm instead of Z-fail" );
+idCVar r_useStencilShadowPreload( "r_useStencilShadowPreload", "0", CVAR_RENDERER | CVAR_BOOL, "use stencil shadow preload algorithm instead of Z-fail" );
 idCVar r_skipShaderPasses( "r_skipShaderPasses", "0", CVAR_RENDERER | CVAR_BOOL, "" );
 idCVar r_skipInteractionFastPath( "r_skipInteractionFastPath", "1", CVAR_RENDERER | CVAR_BOOL, "" );
 idCVar r_useLightStencilSelect( "r_useLightStencilSelect", "0", CVAR_RENDERER | CVAR_BOOL, "use stencil select pass" );
diff --git a/neo/renderer/Vulkan/RenderBackend_VK.cpp b/neo/renderer/Vulkan/RenderBackend_VK.cpp
index ea110ced..13109276 100644
--- a/neo/renderer/Vulkan/RenderBackend_VK.cpp
+++ b/neo/renderer/Vulkan/RenderBackend_VK.cpp
@@ -2321,7 +2321,11 @@ void idRenderBackend::DrawStencilShadowPass( const drawSurf_t* drawSurf, const b
 	}
 	else
 	{
-		// Z-fail
+		// Z-fail (Carmack's Reverse)
+		uint64 stencil = GLS_STENCIL_OP_FAIL_KEEP | GLS_STENCIL_OP_ZFAIL_DECR | GLS_STENCIL_OP_PASS_KEEP
+						 | GLS_BACK_STENCIL_OP_FAIL_KEEP | GLS_BACK_STENCIL_OP_ZFAIL_INCR | GLS_BACK_STENCIL_OP_PASS_KEEP;
+
+		GL_State( ( glStateBits & ~GLS_STENCIL_OP_BITS ) | stencil );
 	}
 
 	// get vertex buffer