diff --git a/src/gl/scene/gl_drawinfo.cpp b/src/gl/scene/gl_drawinfo.cpp
index 1d3936948..842423094 100644
--- a/src/gl/scene/gl_drawinfo.cpp
+++ b/src/gl/scene/gl_drawinfo.cpp
@@ -325,6 +325,7 @@ void GLDrawList::SortWallIntoPlane(SortNode * head,SortNode * sort)
 		if (gl.glslversion < 1.3f)
 		{
 			GLWall * ws1;
+			ws->vertcount = 0;	// invalidate current vertices.
 			ws1=&walls[walls.Size()-1];
 			ws=&walls[drawitems[sort->itemindex].index];	// may have been reallocated!
 			float newtexv = ws->tcs[GLWall::UPLFT].v + ((ws->tcs[GLWall::LOLFT].v - ws->tcs[GLWall::UPLFT].v) / (ws->zbottom[0] - ws->ztop[0])) * (fh->z - ws->ztop[0]);
@@ -467,6 +468,7 @@ void GLDrawList::SortWallIntoWall(SortNode * head,SortNode * sort)
 		float izt=(float)(ws->ztop[0]+r*(ws->ztop[1]-ws->ztop[0]));
 		float izb=(float)(ws->zbottom[0]+r*(ws->zbottom[1]-ws->zbottom[0]));
 
+		ws->vertcount = 0;	// invalidate current vertices.
 		GLWall w=*ws;
 		AddWall(&w);
 		ws1=&walls[walls.Size()-1];
diff --git a/src/gl/scene/gl_scene.cpp b/src/gl/scene/gl_scene.cpp
index 24fd9a678..ef82472e0 100644
--- a/src/gl/scene/gl_scene.cpp
+++ b/src/gl/scene/gl_scene.cpp
@@ -526,7 +526,7 @@ void gl_FillScreen()
 	gl_RenderState.EnableTexture(false);
 	gl_RenderState.Apply();
 	// The fullscreen quad is stored at index 4 in the main vertex buffer.
-	glDrawArrays(GL_TRIANGLE_STRIP, 4, 4);
+	glDrawArrays(GL_TRIANGLE_STRIP, FFlatVertexBuffer::FULLSCREEN_INDEX, 4);
 }
 
 //==========================================================================
diff --git a/src/gl/scene/gl_walls.cpp b/src/gl/scene/gl_walls.cpp
index 54ba8c731..3afde063c 100644
--- a/src/gl/scene/gl_walls.cpp
+++ b/src/gl/scene/gl_walls.cpp
@@ -135,6 +135,7 @@ void GLWall::PutWall(bool translucent)
 	if (translucent) // translucent walls
 	{
 		ViewDistance = (ViewPos - (seg->linedef->v1->fPos() + seg->linedef->Delta() / 2)).XY().LengthSquared();
+		if (gl.buffermethod == BM_DEFERRED) MakeVertices(true);
 		gl_drawinfo->drawlists[GLDL_TRANSLUCENT].AddWall(this);
 	}
 	else
@@ -157,16 +158,19 @@ void GLWall::PutWall(bool translucent)
 		{
 			list = masked ? GLDL_MASKEDWALLS : GLDL_PLAINWALLS;
 		}
+		if (gl.buffermethod == BM_DEFERRED) MakeVertices(false);
 		gl_drawinfo->drawlists[list].AddWall(this);
 
 	}
 	lightlist = NULL;
+	vertcount = 0;	// make sure that following parts of the same linedef do not get this one's vertex info.
 }
 
 void GLWall::PutPortal(int ptype)
 {
 	GLPortal * portal;
 
+	if (gl.buffermethod == BM_DEFERRED) MakeVertices(false);
 	switch (ptype)
 	{
 	// portals don't go into the draw list.
@@ -237,6 +241,7 @@ void GLWall::PutPortal(int ptype)
 		portal->AddLine(this);
 		break;
 	}
+	vertcount = 0;
 }
 //==========================================================================
 //