diff --git a/src/bigint.rs b/src/bigint.rs
index 3c1c087..a585f55 100644
--- a/src/bigint.rs
+++ b/src/bigint.rs
@@ -372,7 +372,7 @@ impl Rem<BigUint, BigUint> for BigUint {
 
 impl Neg<BigUint> for BigUint {
     #[inline]
-    fn neg(&self) -> BigUint { fail!() }
+    fn neg(&self) -> BigUint { panic!() }
 }
 
 impl CheckedAdd for BigUint {
@@ -428,7 +428,7 @@ impl Integer for BigUint {
     }
 
     fn div_mod_floor(&self, other: &BigUint) -> (BigUint, BigUint) {
-        if other.is_zero() { fail!() }
+        if other.is_zero() { panic!() }
         if self.is_zero() { return (Zero::zero(), Zero::zero()); }
         if *other == One::one() { return ((*self).clone(), Zero::zero()); }
 
@@ -838,7 +838,7 @@ fn get_radix_base(radix: uint) -> (DoubleBigDigit, uint) {
         14 => (1475789056, 8),
         15 => (2562890625, 8),
         16 => (4294967296, 8),
-        _  => fail!("The radix must be within (1, 16]")
+        _  => panic!("The radix must be within (1, 16]")
     }
 }
 
@@ -1093,7 +1093,7 @@ impl Integer for BigInt {
         let d = BigInt::from_biguint(Plus, d_ui);
         let r = BigInt::from_biguint(Plus, r_ui);
         match (self.sign, other.sign) {
-            (_,    NoSign)   => fail!(),
+            (_,    NoSign)   => panic!(),
             (Plus, Plus)  | (NoSign, Plus)  => ( d,  r),
             (Plus, Minus) | (NoSign, Minus) => (-d,  r),
             (Minus, Plus)                 => (-d, -r),
@@ -1119,7 +1119,7 @@ impl Integer for BigInt {
         let d = BigInt::from_biguint(Plus, d_ui);
         let m = BigInt::from_biguint(Plus, m_ui);
         match (self.sign, other.sign) {
-            (_,    NoSign)   => fail!(),
+            (_,    NoSign)   => panic!(),
             (Plus, Plus)  | (NoSign, Plus)  => (d, m),
             (Plus, Minus) | (NoSign, Minus) => if m.is_zero() {
                 (-d, Zero::zero())
@@ -2131,7 +2131,7 @@ mod biguint_tests {
             (10, match bits {
                 32 => "8589934593".to_string(),
                 16 => "131073".to_string(),
-                _ => fail!()
+                _ => panic!()
             }),
             (16,
              format!("2{}1", "0".repeat(bits / 4 - 1)))
@@ -2147,7 +2147,7 @@ mod biguint_tests {
             (10, match bits {
                 32 => "55340232229718589441".to_string(),
                 16 => "12885032961".to_string(),
-                _ => fail!()
+                _ => panic!()
             }),
             (16,
              format!("3{}2{}1",
@@ -2206,7 +2206,7 @@ mod biguint_tests {
         fn check(n: uint, s: &str) {
             let n = factor(n);
             let ans = match FromStrRadix::from_str_radix(s, 10) {
-                Some(x) => x, None => fail!()
+                Some(x) => x, None => panic!()
             };
             assert_eq!(n, ans);
         }
diff --git a/src/rational.rs b/src/rational.rs
index 89a5bd7..213f930 100644
--- a/src/rational.rs
+++ b/src/rational.rs
@@ -54,7 +54,7 @@ impl<T: Clone + Integer + PartialOrd>
     #[inline]
     pub fn new(numer: T, denom: T) -> Ratio<T> {
         if denom == Zero::zero() {
-            fail!("denominator == 0");
+            panic!("denominator == 0");
         }
         let mut ret = Ratio::new_raw(numer, denom);
         ret.reduce();