diff --git a/src/device/video_sdl2.rs b/src/device/video_sdl2.rs
index 6da48a8..63fce54 100644
--- a/src/device/video_sdl2.rs
+++ b/src/device/video_sdl2.rs
@@ -46,13 +46,13 @@ impl Sdl2VideoDevice {
 
     fn clear(&mut self) {
         {
-            let fg = self.fg.borrow_mut();
+            let mut fg = self.fg.borrow_mut();
             for i in 0..(self.width * self.height) as usize {
                 fg.pixels[i] = 0x00;
             }
         }
         {
-            let bg = self.bg.borrow_mut();
+            let mut bg = self.bg.borrow_mut();
             for i in 0..(self.width * self.height) as usize {
                 bg.pixels[i] = 0x00;
             }
@@ -63,7 +63,7 @@ impl Sdl2VideoDevice {
      * Update an entry in either the foreground or background buffers, marking the buffer as dirty.
      */
     fn write_pixel(&mut self, layer: bool, x: u16, y: u16, color: u8) {
-        let layer = if layer {
+        let mut layer = if layer {
             self.fg.borrow_mut()
         } else {
             self.bg.borrow_mut()