diff --git a/src/gl/data/gl_vertexbuffer.cpp b/src/gl/data/gl_vertexbuffer.cpp
index 05fd475c0..7e7784954 100644
--- a/src/gl/data/gl_vertexbuffer.cpp
+++ b/src/gl/data/gl_vertexbuffer.cpp
@@ -153,7 +153,7 @@ FFlatVertexBuffer::FFlatVertexBuffer(int width, int height)
 		map = new FFlatVertex[BUFFER_SIZE];
 	}
 	mIndex = mCurIndex = 0;
-	mNumReserved = 12;
+	mNumReserved = NUM_RESERVED;
 	vbo_shadowdata.Resize(mNumReserved);
 
 	// the first quad is reserved for handling coordinates through uniforms.
@@ -174,6 +174,17 @@ FFlatVertexBuffer::FFlatVertexBuffer(int width, int height)
 	vbo_shadowdata[10].Set(1.0f, -1.0f, 0, 1.f, 0.0f);
 	vbo_shadowdata[11].Set(1.0f, 1.0f, 0, 1.f, 1.f);
 
+	// The next two are the stencil caps.
+	vbo_shadowdata[12].Set(-32767.0f, 32767.0f, -32767.0f, 0, 0);
+	vbo_shadowdata[13].Set(-32767.0f, 32767.0f, 32767.0f, 0, 0);
+	vbo_shadowdata[14].Set(32767.0f, 32767.0f, 32767.0f, 0, 0);
+	vbo_shadowdata[15].Set(32767.0f, 32767.0f, -32767.0f, 0, 0);
+
+	vbo_shadowdata[16].Set(-32767.0f, -32767.0f, -32767.0f, 0, 0);
+	vbo_shadowdata[17].Set(-32767.0f, -32767.0f, 32767.0f, 0, 0);
+	vbo_shadowdata[18].Set(32767.0f, -32767.0f, 32767.0f, 0, 0);
+	vbo_shadowdata[19].Set(32767.0f, -32767.0f, -32767.0f, 0, 0);
+
 }
 
 FFlatVertexBuffer::~FFlatVertexBuffer()
diff --git a/src/gl/data/gl_vertexbuffer.h b/src/gl/data/gl_vertexbuffer.h
index 5e6912a10..68f101367 100644
--- a/src/gl/data/gl_vertexbuffer.h
+++ b/src/gl/data/gl_vertexbuffer.h
@@ -87,7 +87,11 @@ public:
 	{
 		QUAD_INDEX = 0,
 		FULLSCREEN_INDEX = 4,
-		PRESENT_INDEX = 8
+		PRESENT_INDEX = 8,
+		STENCILTOP_INDEX = 12,
+		STENCILBOTTOM_INDEX = 16,
+
+		NUM_RESERVED = 20
 	};
 
 	TArray<FFlatVertex> vbo_shadowdata;	// this is kept around for updating the actual (non-readable) buffer and as stand-in for pre GL 4.x
diff --git a/src/gl/scene/gl_portal.cpp b/src/gl/scene/gl_portal.cpp
index bb7166805..628e0f915 100644
--- a/src/gl/scene/gl_portal.cpp
+++ b/src/gl/scene/gl_portal.cpp
@@ -147,40 +147,25 @@ void GLPortal::DrawPortalStencil()
 {
 	if (mPrimIndices.Size() == 0)
 	{
-		bool cap = NeedCap() && lines.Size() > 1;
-		mPrimIndices.Resize(2 * lines.Size() + 4 * cap);
+		mPrimIndices.Resize(2 * lines.Size());
 
-		for (unsigned int i = 0; i<lines.Size(); i++)
+		for (unsigned int i = 0; i < lines.Size(); i++)
 		{
 			if (gl.buffermethod != BM_DEFERRED) lines[i].MakeVertices(false);
 			mPrimIndices[i * 2] = lines[i].vertindex;
 			mPrimIndices[i * 2 + 1] = lines[i].vertcount;
 		}
-
-		if (cap)
-		{
-			// Cap the stencil at the top and bottom
-			int n = lines.Size() * 2;
-			FFlatVertex *ptr = GLRenderer->mVBO->GetBuffer();
-			ptr[0].Set(-32767.0f, 32767.0f, -32767.0f, 0, 0);
-			ptr[1].Set(-32767.0f, 32767.0f, 32767.0f, 0, 0);
-			ptr[2].Set(32767.0f, 32767.0f, 32767.0f, 0, 0);
-			ptr[3].Set(32767.0f, 32767.0f, -32767.0f, 0, 0);
-			ptr += 4;
-			mPrimIndices[n + 1] = GLRenderer->mVBO->GetCount(ptr, &mPrimIndices[n]);
-			ptr[0].Set(-32767.0f, -32767.0f, -32767.0f, 0, 0);
-			ptr[1].Set(-32767.0f, -32767.0f, 32767.0f, 0, 0);
-			ptr[2].Set(32767.0f, -32767.0f, 32767.0f, 0, 0);
-			ptr[3].Set(32767.0f, -32767.0f, -32767.0f, 0, 0);
-			ptr += 4;
-			mPrimIndices[n + 3] = GLRenderer->mVBO->GetCount(ptr, &mPrimIndices[n + 2]);
-		}
 	}
 	gl_RenderState.Apply();
 	for (unsigned int i = 0; i < mPrimIndices.Size(); i += 2)
 	{
 		GLRenderer->mVBO->RenderArray(GL_TRIANGLE_FAN, mPrimIndices[i], mPrimIndices[i + 1]);
 	}
+	if (NeedCap() && lines.Size() > 1)
+	{
+		glDrawArrays(GL_TRIANGLE_FAN, FFlatVertexBuffer::STENCILTOP_INDEX, 4);
+		glDrawArrays(GL_TRIANGLE_FAN, FFlatVertexBuffer::STENCILBOTTOM_INDEX, 4);
+	}
 }