diff --git a/complex/src/lib.rs b/complex/src/lib.rs
index 8a3718f..62f74cc 100644
--- a/complex/src/lib.rs
+++ b/complex/src/lib.rs
@@ -33,7 +33,7 @@ use traits::{Zero, One, Num, Float};
 // probably doesn't map to C's _Complex correctly.
 
 /// A complex number in Cartesian form.
-#[derive(PartialEq, Copy, Clone, Hash, Debug, Default)]
+#[derive(PartialEq, Eq, Copy, Clone, Hash, Debug, Default)]
 #[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
 pub struct Complex<T> {
     /// Real portion of the complex number
@@ -1220,6 +1220,20 @@ mod test {
         assert!(::hash(&c) != ::hash(&a));
     }
 
+    #[test]
+    fn test_hashset() {
+        use std::collections::HashSet;
+        let a = Complex::new(0i32, 0i32);
+        let b = Complex::new(1i32, 0i32);
+        let c = Complex::new(0i32, 1i32);
+
+        let set: HashSet<_> = [a, b, c].iter().cloned().collect();
+        assert!(set.contains(&a));
+        assert!(set.contains(&b));
+        assert!(set.contains(&c));
+        assert!(!set.contains(&(a + b + c)));
+    }
+
     #[test]
     fn test_is_nan() {
         assert!(!_1_1i.is_nan());