diff --git a/components/canvas/canvas_paint_task.rs b/components/canvas/canvas_paint_task.rs
index c2921561c49..28a3a22b563 100644
--- a/components/canvas/canvas_paint_task.rs
+++ b/components/canvas/canvas_paint_task.rs
@@ -594,7 +594,7 @@ impl<'a> CanvasPaintTask<'a> {
 
     fn put_image_data(&mut self, mut imagedata: Vec<u8>,
                       image_data_rect: Rect<f64>,
-                      dirty_rect: Option<Rect<f64>>) {
+                      dirty_rect: Rect<f64>) {
 
         if image_data_rect.size.width <= 0.0 || image_data_rect.size.height <= 0.0 {
             return
@@ -604,18 +604,9 @@ impl<'a> CanvasPaintTask<'a> {
         // rgba -> bgra
         byte_swap(&mut imagedata);
 
-        let image_rect = Rect::new(Point2D::zero(),
-                                   Size2D::new(image_data_rect.size.width, image_data_rect.size.height));
-
         // Dirty rectangle defines the area of the source image to be copied
         // on the destination canvas
-        let source_rect = match dirty_rect {
-            Some(dirty_rect) =>
-                self.calculate_dirty_rect(dirty_rect, image_data_rect),
-            // If no dirty area is provided we consider the whole source image
-            // as the area to be copied to the canvas
-            None => image_rect,
-        };
+        let source_rect = self.calculate_dirty_rect(dirty_rect, image_data_rect);
 
         // 5) If either dirtyWidth or dirtyHeight is negative or zero,
         // stop without affecting any bitmaps
diff --git a/components/canvas_traits/lib.rs b/components/canvas_traits/lib.rs
index 48cabed045c..f7abcb49dee 100644
--- a/components/canvas_traits/lib.rs
+++ b/components/canvas_traits/lib.rs
@@ -91,7 +91,7 @@ pub enum Canvas2dMsg {
     GetImageData(Rect<f64>, Size2D<f64>, IpcSender<Vec<u8>>),
     LineTo(Point2D<f32>),
     MoveTo(Point2D<f32>),
-    PutImageData(Vec<u8>, Rect<f64>, Option<Rect<f64>>),
+    PutImageData(Vec<u8>, Rect<f64>, Rect<f64>),
     QuadraticCurveTo(Point2D<f32>, Point2D<f32>),
     Rect(Rect<f32>),
     RestoreContext,
diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index c9f8da05bff..89ec6a66119 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -929,8 +929,8 @@ impl<'a> CanvasRenderingContext2DMethods for &'a CanvasRenderingContext2D {
         let image_data_rect = Rect::new(Point2D::new(*dx, *dy),
                                         Size2D::new(imagedata.Width() as f64,
                                                     imagedata.Height() as f64));
-        let dirty_rect = Some(Rect::new(Point2D::new(*dirtyX, *dirtyY),
-                                        Size2D::new(*dirtyWidth, *dirtyHeight)));
+        let dirty_rect = Rect::new(Point2D::new(*dirtyX, *dirtyY),
+                                   Size2D::new(*dirtyWidth, *dirtyHeight));
         let msg = CanvasMsg::Canvas2d(Canvas2dMsg::PutImageData(data, image_data_rect, dirty_rect));
         self.ipc_renderer.send(msg).unwrap();
         self.mark_as_dirty();