diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index 7d0acea2dac..d33c634b2b7 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -142,8 +142,15 @@ impl IOCompositor {
                constellation_chan: ConstellationChan,
                time_profiler_chan: TimeProfilerChan,
                memory_profiler_chan: MemoryProfilerChan) -> IOCompositor {
+
+        let scale_factor = match opts.device_pixels_per_px {
+            Some(device_pixels_per_px) => device_pixels_per_px,
+            None => ScaleFactor(1.0),
+        };
+        let framebuffer_size = opts.initial_window_size.as_f32() * scale_factor;
+
         let window: Rc<Window> = WindowMethods::new(app, opts.output_file.is_none(),
-                                                    opts.initial_window_size);
+                                                    framebuffer_size.as_uint());
 
         // Create an initial layer tree.
         //
diff --git a/components/util/opts.rs b/components/util/opts.rs
index f243a3a7b00..677adba2592 100644
--- a/components/util/opts.rs
+++ b/components/util/opts.rs
@@ -89,7 +89,7 @@ pub struct Opts {
     pub devtools_server: bool,
 
     /// The initial requested size of the window.
-    pub initial_window_size: TypedSize2D<DevicePixel, uint>,
+    pub initial_window_size: TypedSize2D<ScreenPx, uint>,
 }
 
 fn print_usage(app: &str, opts: &[getopts::OptGroup]) {