diff --git a/src/cgmath/angle.rs b/src/cgmath/angle.rs
index dbea325..9b7defc 100644
--- a/src/cgmath/angle.rs
+++ b/src/cgmath/angle.rs
@@ -204,8 +204,8 @@ Angle<S> for Deg<S> {
 #[inline] pub fn atan<S: Float>(s: S) -> Rad<S> { rad(s.atan()) }
 #[inline] pub fn atan2<S: Float>(a: S, b: S) -> Rad<S> { rad(a.atan2(&b)) }
 
-impl<S: Float + fmt::Default> ToStr for Rad<S> { fn to_str(&self) -> ~str { format!("{} rad", self.s) } }
-impl<S: Float + fmt::Default> ToStr for Deg<S> { fn to_str(&self) -> ~str { format!("{}°", self.s) } }
+impl<S: Float + fmt::Show> ToStr for Rad<S> { fn to_str(&self) -> ~str { format!("{} rad", self.s) } }
+impl<S: Float + fmt::Show> ToStr for Deg<S> { fn to_str(&self) -> ~str { format!("{}°", self.s) } }
 
 impl<S: Float + ApproxEq<S>>
 ApproxEq<S> for Rad<S> {
diff --git a/src/cgmath/point.rs b/src/cgmath/point.rs
index a9ff458..2c3fea8 100644
--- a/src/cgmath/point.rs
+++ b/src/cgmath/point.rs
@@ -99,13 +99,13 @@ array!(impl<S> Point3<S> -> [S, ..3] _3)
 impl<S: Primitive> Point<S, Vec2<S>, [S, ..2]> for Point2<S> {}
 impl<S: Primitive> Point<S, Vec3<S>, [S, ..3]> for Point3<S> {}
 
-impl<S: fmt::Default> ToStr for Point2<S> {
+impl<S: fmt::Show> ToStr for Point2<S> {
     fn to_str(&self) -> ~str {
         format!("[{}, {}]", self.x, self.y)
     }
 }
 
-impl<S: fmt::Default> ToStr for Point3<S> {
+impl<S: fmt::Show> ToStr for Point3<S> {
     fn to_str(&self) -> ~str {
         format!("[{}, {}, {}]", self.x, self.y, self.z)
     }
diff --git a/src/cgmath/quaternion.rs b/src/cgmath/quaternion.rs
index 5670166..8790a78 100644
--- a/src/cgmath/quaternion.rs
+++ b/src/cgmath/quaternion.rs
@@ -280,7 +280,7 @@ Neg<Quat<S>> for Quat<S> {
     }
 }
 
-impl<S: fmt::Default> ToStr for Quat<S> {
+impl<S: fmt::Show> ToStr for Quat<S> {
     fn to_str(&self) -> ~str {
         format!("{} + {}i + {}j + {}k", self.s, self.v.x, self.v.y, self.v.z)
     }
diff --git a/src/cgmath/transform.rs b/src/cgmath/transform.rs
index d262b6e..6a001b6 100644
--- a/src/cgmath/transform.rs
+++ b/src/cgmath/transform.rs
@@ -157,7 +157,7 @@ ToMat4<S> for Decomposed<S, Vec3<S>, R> {
 impl<S: Float + ApproxEq<S>, R: Rotation3<S>>
 Transform3<S> for Decomposed<S,Vec3<S>,R> {}
 
-impl<S: fmt::Default + Float, R: ToStr + Rotation3<S>>
+impl<S: fmt::Show + Float, R: ToStr + Rotation3<S>>
 ToStr for Decomposed<S,Vec3<S>,R> {
     fn to_str(&self) -> ~str {
         format!("(scale({}), rot({:s}), disp{:s})",
diff --git a/src/cgmath/vector.rs b/src/cgmath/vector.rs
index dadcb09..83bceb9 100644
--- a/src/cgmath/vector.rs
+++ b/src/cgmath/vector.rs
@@ -301,19 +301,19 @@ EuclideanVector<S, [S, ..4]> for Vec4<S> {
     }
 }
 
-impl<S: fmt::Default> ToStr for Vec2<S> {
+impl<S: fmt::Show> ToStr for Vec2<S> {
     fn to_str(&self) -> ~str {
         format!("[{}, {}]", self.x, self.y)
     }
 }
 
-impl<S: fmt::Default> ToStr for Vec3<S> {
+impl<S: fmt::Show> ToStr for Vec3<S> {
     fn to_str(&self) -> ~str {
         format!("[{}, {}, {}]", self.x, self.y, self.z)
     }
 }
 
-impl<S: fmt::Default> ToStr for Vec4<S> {
+impl<S: fmt::Show> ToStr for Vec4<S> {
     fn to_str(&self) -> ~str {
         format!("[{}, {}, {}, {}]", self.x, self.y, self.z, self.w)
     }