diff --git a/src/cgmath/projection.rs b/src/cgmath/projection.rs
index c308e26..3eb305f 100644
--- a/src/cgmath/projection.rs
+++ b/src/cgmath/projection.rs
@@ -214,9 +214,9 @@ impl<S: Float> Projection<S> for Ortho<S> {
 
 impl<S: Float> ToMat4<S> for Ortho<S> {
     fn to_mat4(&self) -> Mat4<S> {
-        assert!(self.left   > self.right, "`left` cannot be greater than `right`, found: left: {:?} right: {:?}", self.left, self.right);
-        assert!(self.bottom > self.top,   "`bottom` cannot be greater than `top`, found: bottom: {:?} top: {:?}", self.bottom, self.top);
-        assert!(self.near   > self.far,   "`near` cannot be greater than `far`, found: near: {:?} far: {:?}", self.near, self.far);
+        assert!(self.left   < self.right, "`left` cannot be greater than `right`, found: left: {:?} right: {:?}", self.left, self.right);
+        assert!(self.bottom < self.top,   "`bottom` cannot be greater than `top`, found: bottom: {:?} top: {:?}", self.bottom, self.top);
+        assert!(self.near   < self.far,   "`near` cannot be greater than `far`, found: near: {:?} far: {:?}", self.near, self.far);
 
         let two: S = cast(2).unwrap();