diff --git a/src/length.rs b/src/length.rs
index 726fd3a..393df56 100644
--- a/src/length.rs
+++ b/src/length.rs
@@ -26,7 +26,7 @@ use std::ops::{Add, Sub, Mul, Div, Neg};
 ///
 /// You can multiply a Length by a `scale_factor::ScaleFactor` to convert it from one unit to
 /// another.  See the ScaleFactor docs for an example.
-#[derive(Copy, RustcDecodable, RustcEncodable, Show)]
+#[derive(Copy, RustcDecodable, RustcEncodable, Debug)]
 pub struct Length<Unit, T>(pub T);
 
 impl<Unit, T: Clone> Length<Unit, T> {
@@ -124,9 +124,9 @@ mod tests {
     use scale_factor::ScaleFactor;
     use std::num::Zero;
 
-    #[derive(Show)]
+    #[derive(Debug)]
     enum Inch {}
-    #[derive(Show)]
+    #[derive(Debug)]
     enum Mm {}
 
     #[test]
diff --git a/src/lib.rs b/src/lib.rs
index 887f1bd..4d67004 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -11,7 +11,7 @@
 #![crate_type = "rlib"]
 
 #![feature(asm, simd)]
-#![allow(unstable)]
+#![feature(core, rustc_private, rand, hash, test)]
 
 #[macro_use]
 extern crate log;
diff --git a/src/matrix.rs b/src/matrix.rs
index 71323c7..b09b44d 100644
--- a/src/matrix.rs
+++ b/src/matrix.rs
@@ -28,7 +28,7 @@ pub fn Matrix4<T:Add<T, Output=T> + Clone + ApproxEq<T> + Mul<T, Output=T> + One
     }
 }
 
-#[derive(Show, Copy)]
+#[derive(Debug, Copy)]
 pub struct Matrix4<T> {
     pub m11: T, pub m12: T, pub m13: T, pub m14: T,
     pub m21: T, pub m22: T, pub m23: T, pub m24: T,
diff --git a/src/point.rs b/src/point.rs
index 62b1213..06d2c07 100644
--- a/src/point.rs
+++ b/src/point.rs
@@ -27,7 +27,7 @@ impl<T: Zero> Point2D<T> {
     }
 }
 
-impl<T: fmt::Show> fmt::Show for Point2D<T> {
+impl<T: fmt::Debug> fmt::Debug for Point2D<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "({:?},{:?})", self.x, self.y)
     }
diff --git a/src/rect.rs b/src/rect.rs
index b16d1f5..8e3996d 100644
--- a/src/rect.rs
+++ b/src/rect.rs
@@ -23,7 +23,7 @@ pub struct Rect<T> {
     pub size: Size2D<T>,
 }
 
-impl<T: fmt::Show> fmt::Show for Rect<T> {
+impl<T: fmt::Debug> fmt::Debug for Rect<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "Rect({:?} at {:?})", self.size, self.origin)
     }
diff --git a/src/scale_factor.rs b/src/scale_factor.rs
index 73845a2..69acb6b 100644
--- a/src/scale_factor.rs
+++ b/src/scale_factor.rs
@@ -31,7 +31,7 @@ use std::ops::{Add, Mul, Sub, Div};
 /// let one_foot: Length<Inch, f32> = Length(12.0);
 /// let one_foot_in_mm: Length<Mm, f32> = one_foot * mm_per_inch;
 /// ```
-#[derive(Copy, RustcDecodable, RustcEncodable, Show)]
+#[derive(Copy, RustcDecodable, RustcEncodable, Debug)]
 pub struct ScaleFactor<Src, Dst, T>(pub T);
 
 impl<Src, Dst, T: Clone> ScaleFactor<Src, Dst, T> {
@@ -104,11 +104,11 @@ impl<Src, Dst, T: Clone> Clone for ScaleFactor<Src, Dst, T> {
 mod tests {
     use super::ScaleFactor;
 
-    #[derive(Show)]
+    #[derive(Debug)]
     enum Inch {}
-    #[derive(Show)]
+    #[derive(Debug)]
     enum Cm {}
-    #[derive(Show)]
+    #[derive(Debug)]
     enum Mm {}
 
     #[test]
diff --git a/src/size.rs b/src/size.rs
index 9377cfc..75740b2 100644
--- a/src/size.rs
+++ b/src/size.rs
@@ -20,7 +20,7 @@ pub struct Size2D<T> {
     pub height: T
 }
 
-impl<T: fmt::Show> fmt::Show for Size2D<T> {
+impl<T: fmt::Debug> fmt::Debug for Size2D<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?}×{:?}", self.width, self.height)
     }