diff --git a/Cargo.toml b/Cargo.toml
index 8325fa147a..59dc8cbc8c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,12 +17,17 @@ complex, rational, range iterators, generic integers, and more!
 rustc-serialize = { version = "0.3.13", optional = true }
 rand = { version = "0.3.8", optional = true }
 
+[dev-dependencies]
+# Some tests of non-rand functionality still use rand because the tests
+# themselves are randomized.
+rand = { version = "0.3.8" }
+
 [features]
 
 complex = []
 rational = []
-bigint = ["rustc-serialize", "rand"]
-default = ["complex", "rational", "bigint"]
+bigint = []
+default = ["bigint", "complex", "rand", "rational", "rustc-serialize"]
 
 [[bench]]
 name = "bigint"
diff --git a/src/bigint.rs b/src/bigint.rs
index a4256fb0cc..c6978507c7 100644
--- a/src/bigint.rs
+++ b/src/bigint.rs
@@ -43,6 +43,8 @@
 //! ```rust
 //! extern crate rand;
 //! extern crate num;
+//!
+//! # #[cfg(feature = "rand")]
 //! # fn main() {
 //! use num::bigint::{ToBigInt, RandBigInt};
 //!
@@ -56,6 +58,10 @@
 //! // Probably an even larger number.
 //! println!("{}", a * b);
 //! # }
+//!
+//! # #[cfg(not(feature = "rand"))]
+//! # fn main() {
+//! # }
 //! ```
 
 use Integer;
@@ -71,6 +77,10 @@ use std::cmp::Ordering::{self, Less, Greater, Equal};
 use std::{f32, f64};
 use std::{u8, i64, u64};
 
+// Some of the tests of non-RNG-based functionality are randomized using the
+// RNG-based functionality, so the RNG-based functionality needs to be enabled
+// for tests.
+#[cfg(any(feature = "rand", test))]
 use rand::Rng;
 
 use traits::{ToPrimitive, FromPrimitive};
@@ -173,11 +183,13 @@ fn div_wide(hi: BigDigit, lo: BigDigit, divisor: BigDigit) -> (BigDigit, BigDigi
     let rhs = divisor as DoubleBigDigit;
     ((lhs / rhs) as BigDigit, (lhs % rhs) as BigDigit)
 }
+
 /// A big unsigned integer type.
 ///
 /// A `BigUint`-typed value `BigUint { data: vec!(a, b, c) }` represents a number
 /// `(a + b * big_digit::BASE + c * big_digit::BASE^2)`.
-#[derive(Clone, RustcEncodable, RustcDecodable, Debug, Hash)]
+#[derive(Clone, Debug, Hash)]
+#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
 pub struct BigUint {
     data: Vec<BigDigit>
 }
@@ -1729,7 +1741,8 @@ fn get_radix_base(radix: u32) -> (DoubleBigDigit, usize) {
 }
 
 /// A Sign is a `BigInt`'s composing element.
-#[derive(PartialEq, PartialOrd, Eq, Ord, Copy, Clone, Debug, RustcEncodable, RustcDecodable, Hash)]
+#[derive(PartialEq, PartialOrd, Eq, Ord, Copy, Clone, Debug, Hash)]
+#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
 pub enum Sign { Minus, NoSign, Plus }
 
 impl Neg for Sign {
@@ -1760,7 +1773,8 @@ impl Mul<Sign> for Sign {
 }
 
 /// A big signed integer type.
-#[derive(Clone, RustcEncodable, RustcDecodable, Debug, Hash)]
+#[derive(Clone, Debug, Hash)]
+#[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
 pub struct BigInt {
     sign: Sign,
     data: BigUint
@@ -2387,6 +2401,7 @@ pub trait RandBigInt {
     fn gen_bigint_range(&mut self, lbound: &BigInt, ubound: &BigInt) -> BigInt;
 }
 
+#[cfg(any(feature = "rand", test))]
 impl<R: Rng> RandBigInt for R {
     fn gen_biguint(&mut self, bit_size: usize) -> BigUint {
         let (digits, rem) = bit_size.div_rem(&big_digit::BITS);
diff --git a/src/lib.rs b/src/lib.rs
index b8c8aa7360..3902ae9351 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -59,7 +59,11 @@
 
 #[cfg(feature = "rustc-serialize")]
 extern crate rustc_serialize;
-#[cfg(feature = "rand")]
+
+// Some of the tests of non-RNG-based functionality are randomized using the
+// RNG-based functionality, so the RNG-based functionality needs to be enabled
+// for tests.
+#[cfg(any(feature = "rand", all(feature = "bigint", test)))]
 extern crate rand;
 
 #[cfg(feature = "bigint")]