diff --git a/src/lib.rs b/src/lib.rs
index 0edaac0..02b50f6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -50,7 +50,21 @@ impl Mul for Fr {
     fn mul(self, other: Fr) -> Fr { Fr(self.0 * other.0) }
 }
 
-pub trait Group: 'static + Send + Copy + Clone + PartialEq + Eq + Sized + Add<Self, Output=Self> + Sub<Self, Output=Self> + Neg<Output=Self> + Mul<Fr, Output=Self> {
+pub trait Group:
+        rustc_serialize::Encodable +
+        rustc_serialize::Decodable +
+        'static +
+        Send +
+        Copy +
+        Clone +
+        PartialEq +
+        Eq +
+        Sized +
+        Add<Self, Output=Self> +
+        Sub<Self, Output=Self> +
+        Neg<Output=Self> +
+        Mul<Fr, Output=Self>
+{
     fn zero() -> Self;
     fn one() -> Self;
     fn random<R: Rng>(rng: &mut R) -> Self;