diff --git a/src/libnum/bigint.rs b/src/libnum/bigint.rs
index ef6f1aafe88..ac8da664de7 100644
--- a/src/libnum/bigint.rs
+++ b/src/libnum/bigint.rs
@@ -19,6 +19,7 @@ A `BigInt` is a combination of `BigUint` and `Sign`.
 use Integer;
 
 use std::cmp;
+use std::default::Default;
 use std::fmt;
 use std::from_str::FromStr;
 use std::num::CheckedDiv;
@@ -112,6 +113,11 @@ impl TotalOrd for BigUint {
     }
 }
 
+impl Default for BigUint {
+    #[inline]
+    fn default() -> BigUint { BigUint::new(Vec::new()) }
+}
+
 impl fmt::Show for BigUint {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f.buf, "{}", self.to_str_radix(10))
@@ -830,6 +836,11 @@ impl TotalOrd for BigInt {
     }
 }
 
+impl Default for BigInt {
+    #[inline]
+    fn default() -> BigInt { BigInt::new(Zero, Vec::new()) }
+}
+
 impl fmt::Show for BigInt {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f.buf, "{}", self.to_str_radix(10))