diff --git a/Outputs/OpenGL/Primitives/TextureTarget.cpp b/Outputs/OpenGL/Primitives/TextureTarget.cpp
index 747c9c2ef..5a252e898 100644
--- a/Outputs/OpenGL/Primitives/TextureTarget.cpp
+++ b/Outputs/OpenGL/Primitives/TextureTarget.cpp
@@ -41,7 +41,10 @@ TextureTarget::TextureTarget(GLsizei width, GLsizei height, GLenum texture_unit,
 
 	// Also add a stencil buffer if requested.
 	if(has_stencil_buffer) {
+		glGenRenderbuffers(1, &renderbuffer_);
+		glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer_);
 		glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX1, expanded_width_, expanded_height_);
+		glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, renderbuffer_);
 	}
 
 	// Check for successful construction.
@@ -52,6 +55,7 @@ TextureTarget::TextureTarget(GLsizei width, GLsizei height, GLenum texture_unit,
 TextureTarget::~TextureTarget() {
 	glDeleteFramebuffers(1, &framebuffer_);
 	glDeleteTextures(1, &texture_);
+	if(renderbuffer_) glDeleteRenderbuffers(1, &renderbuffer_);
 	if(drawing_vertex_array_) glDeleteVertexArrays(1, &drawing_vertex_array_);
 	if(drawing_array_buffer_) glDeleteBuffers(1, &drawing_array_buffer_);
 }
diff --git a/Outputs/OpenGL/Primitives/TextureTarget.hpp b/Outputs/OpenGL/Primitives/TextureTarget.hpp
index 73801ee83..647275f23 100644
--- a/Outputs/OpenGL/Primitives/TextureTarget.hpp
+++ b/Outputs/OpenGL/Primitives/TextureTarget.hpp
@@ -78,7 +78,7 @@ class TextureTarget {
 		};
 
 	private:
-		GLuint framebuffer_ = 0, texture_ = 0;
+		GLuint framebuffer_ = 0, texture_ = 0, renderbuffer_ = 0;
 		GLsizei width_ = 0, height_ = 0;
 		GLsizei expanded_width_ = 0, expanded_height_ = 0;
 		GLenum texture_unit_ = 0;
diff --git a/Outputs/OpenGL/ScanTarget.cpp b/Outputs/OpenGL/ScanTarget.cpp
index 152f9fe4f..4990c3e64 100644
--- a/Outputs/OpenGL/ScanTarget.cpp
+++ b/Outputs/OpenGL/ScanTarget.cpp
@@ -488,10 +488,11 @@ void ScanTarget::draw(bool synchronous, int output_width, int output_height) {
 	}
 
 	// Ensure the accumulation buffer is properly sized.
-	if(!accumulation_texture_ || (!synchronous && (accumulation_texture_->get_width() != output_width || accumulation_texture_->get_height() != output_height))) {
+	const int proportional_width = (output_height * 4) / 3;
+	if(!accumulation_texture_ || (!synchronous && (accumulation_texture_->get_width() != proportional_width || accumulation_texture_->get_height() != output_height))) {
 		std::unique_ptr<OpenGL::TextureTarget> new_framebuffer(
 			new TextureTarget(
-				GLsizei(output_width),
+				GLsizei(proportional_width),
 				GLsizei(output_height),
 				AccumulationTextureUnit,
 				GL_LINEAR,
@@ -511,6 +512,12 @@ void ScanTarget::draw(bool synchronous, int output_width, int output_height) {
 
 	// Bind the accumulation texture.
 	accumulation_texture_->bind_framebuffer();
+	glClear(GL_STENCIL_BUFFER_BIT);
+
+	// Enable stenciling and ensure spans increment the stencil buffer.
+	glEnable(GL_STENCIL_TEST);
+	glStencilFunc(GL_EQUAL, 0, GLuint(-1));
+	glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
 
 	// Output all lines except the one currently being worked on.
 	glBindVertexArray(line_vertex_array_);
@@ -518,6 +525,10 @@ void ScanTarget::draw(bool synchronous, int output_width, int output_height) {
 	glEnable(GL_BLEND);
 	glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, GLsizei(line_buffer_.size() - 2));
 
+	// Clear untouched parts of the display. (TODO: at vertical sync, probably)
+	full_display_rectangle_.draw(0.0, 0.0, 0.0);
+	glDisable(GL_STENCIL_TEST);
+
 	// Copy the accumulatiion texture to the target (TODO: don't assume framebuffer 0).
 	glBindFramebuffer(GL_FRAMEBUFFER, 0);
 	glViewport(0, 0, (GLsizei)output_width, (GLsizei)output_height);