diff --git a/src/gl/renderer/gl_renderer.cpp b/src/gl/renderer/gl_renderer.cpp
index af910921b..74bd81c17 100644
--- a/src/gl/renderer/gl_renderer.cpp
+++ b/src/gl/renderer/gl_renderer.cpp
@@ -75,7 +75,6 @@
 #include "r_videoscale.h"
 
 EXTERN_CVAR(Int, screenblocks)
-EXTERN_CVAR(Int, vid_scalemode)
 
 CVAR(Bool, gl_scale_viewport, true, CVAR_ARCHIVE);
 
@@ -312,7 +311,10 @@ void FGLRenderer::SetOutputViewport(GL_IRECT *bounds)
 	mSceneViewport.height = height;
 
 	// Scale viewports to fit letterbox
-	if ((gl_scale_viewport && !framebuffer->IsFullscreen() && vid_scalemode == 0) || !FGLRenderBuffers::IsEnabled())
+	bool notScaled = ((mScreenViewport.width == ViewportScaledWidth(mScreenViewport.width, mScreenViewport.height)) &&
+		(mScreenViewport.width == ViewportScaledHeight(mScreenViewport.width, mScreenViewport.height)) &&
+		!ViewportIsScaled43());
+	if ((gl_scale_viewport && !framebuffer->IsFullscreen() && notScaled) || !FGLRenderBuffers::IsEnabled())
 	{
 		mScreenViewport.width = mOutputLetterbox.width;
 		mScreenViewport.height = mOutputLetterbox.height;
diff --git a/src/gl/system/gl_framebuffer.cpp b/src/gl/system/gl_framebuffer.cpp
index 7425271be..d6eb142d8 100644
--- a/src/gl/system/gl_framebuffer.cpp
+++ b/src/gl/system/gl_framebuffer.cpp
@@ -56,7 +56,6 @@
 EXTERN_CVAR (Float, vid_brightness)
 EXTERN_CVAR (Float, vid_contrast)
 EXTERN_CVAR (Bool, vid_vsync)
-EXTERN_CVAR(Int, vid_scalemode)
 
 CVAR(Bool, gl_aalines, false, CVAR_ARCHIVE)