diff --git a/src/angle.rs b/src/angle.rs
index c4a0f93..c2f4df4 100644
--- a/src/angle.rs
+++ b/src/angle.rs
@@ -14,7 +14,9 @@ pub trait Angle<T>: Add<self,self>
                   , Sub<self,self>
                   , Mul<T,self>
                   , Div<T,self>
+                  // , Div<self,T>
                   , Modulo<T,self>
+                  // , Modulo<self,T>
                   , Neg<self>
                   , Eq, Ord {
     static pure fn full_turn() -> self;
@@ -50,7 +52,14 @@ pub impl<T:Copy Num NumCast Eq Ord> Radians<T>: Angle<T> {
     
     #[inline(always)]
     pure fn wrap(&self) -> Radians<T> {
-        (*self) % cast(2.0 * pi)   // TODO: keep in the domain of 0 to two_pi
+        let theta = (*self) % cast(2.0 * pi);
+        
+        // keep in the domain of 0 to 1 rad
+        if theta >= Angle::zero() {
+            theta
+        } else {
+            theta + Angle::full_turn()
+        }
     }
     
     #[inline(always)]
@@ -137,7 +146,14 @@ pub impl<T:Copy Num NumCast Eq Ord> Degrees<T>: Angle<T> {
     
     #[inline(always)]
     pure fn wrap(&self) -> Degrees<T> {
-        (*self) % cast(360)   // TODO: keep in the domain of 0 to 360
+        let theta = (*self) % cast(360);
+        
+        // keep in the domain of 0 to 360 degrees
+        if theta >= Angle::zero() {
+            theta
+        } else {
+            theta + Angle::full_turn()
+        }
     }
     
     #[inline(always)]
diff --git a/src/test/test_angle.rs b/src/test/test_angle.rs
index 3624899..9dd9812 100644
--- a/src/test/test_angle.rs
+++ b/src/test/test_angle.rs
@@ -21,14 +21,14 @@ fn test_radians() {
     assert Radians(pi).wrap()                   == Radians(pi);
     assert Radians(3.0 * pi).wrap()             == Radians(pi);
     assert Radians(2.0 * pi).wrap()             == Radians(0.0);
-    assert Radians(-pi).wrap()                  == Radians(-pi);   // FIXME: should be in the domain of 0 to two_pi
-    assert Radians(-3.0 * pi).wrap()            == Radians(-pi);   // FIXME: should be in the domain of 0 to two_pi
+    assert Radians(-pi).wrap()                  == Radians(pi);
+    assert Radians(-3.0 * pi).wrap()            == Radians(pi);
     assert Radians(-2.0 * pi).wrap()            == Radians(0.0);
     
     assert Radians(0.0).opposite()              == Radians(pi as float);
     assert Radians(pi / 2.0).opposite()         == Radians((pi / 2.0) * 3.0);
     assert Radians(pi * 3.0).opposite()         == Radians(0.0);
-    assert Radians(-2.0 * pi).opposite()        == Radians(-pi);   // FIXME: should be in the domain of 0 to two_pi
+    assert Radians(-2.0 * pi).opposite()        == Radians(pi);
     
     assert Radians(pi) + Radians(pi)            == Radians(2.0 * pi);
     assert Radians(2.0 * pi) - Radians(pi)      == Radians(pi);
@@ -57,14 +57,14 @@ fn test_degrees() {
     assert Degrees(90.0).wrap()                 == Degrees(90.0);
     assert Degrees(450.0).wrap()                == Degrees(90.0);
     assert Degrees(360.0).wrap()                == Degrees(0.0);
-    assert Degrees(-90.0).wrap()                == Degrees(-90.0);   // FIXME: should be in the domain of 0 to 360
-    assert Degrees(-450.0).wrap()               == Degrees(-90.0);   // FIXME: should be in the domain of 0 to 360
+    assert Degrees(-90.0).wrap()                == Degrees(270.0);
+    assert Degrees(-450.0).wrap()               == Degrees(270.0);
     assert Degrees(-360.0).wrap()               == Degrees(0.0);
     
     assert Degrees(0.0).opposite()              == Degrees(180.0);
     assert Degrees(90.0).opposite()             == Degrees(270.0);
     assert Degrees(540.0).opposite()            == Degrees(0.0);
-    assert Degrees(-360.0).opposite()           == Degrees(-180.0);   // FIXME: should be in the domain of 0 to 360
+    assert Degrees(-360.0).opposite()           == Degrees(180.0);
     
     assert Degrees(180.0) + Degrees(180.0)      == Degrees(360.0);
     assert Degrees(360.0) - Degrees(180.0)      == Degrees(180.0);