diff --git a/src/buffers.rs b/src/buffers.rs
index cab4f9a..e259597 100644
--- a/src/buffers.rs
+++ b/src/buffers.rs
@@ -163,7 +163,8 @@ impl<S: Surface + Default> SurfacePool<S> {
 
 impl<S: Surface + Default> Surfaces for SurfacePool<S> {
     type Surface = S;
-    fn new_surface(&mut self, area: &Rectangle<Virtual>) -> Result<S, io::Error> {
+    type Error = io::Error;
+    fn new_surface(&mut self, area: &Rectangle<Virtual>) -> Result<S, Self::Error> {
         let mut surface = S::default();
         surface.set_rect(area);
         self.surfaces.push(surface.clone());
diff --git a/src/render.rs b/src/render.rs
index 9d9b0d3..a77cad0 100644
--- a/src/render.rs
+++ b/src/render.rs
@@ -29,7 +29,8 @@ pub trait Shader: Send + Sync {
 
 pub trait Surfaces: Send + Sync {
     type Surface: Surface;
-    fn new_surface(&mut self, area: &Rectangle<Virtual>) -> Result<Self::Surface, io::Error>;
+    type Error: Debug;
+    fn new_surface(&mut self, area: &Rectangle<Virtual>) -> Result<Self::Surface, Self::Error>;
     fn render_to<S: Sample>(&self, output: &mut S, frame: usize);
 }