diff --git a/src/lib/char.rs b/src/lib/char.rs
index e91e8697dd86e..28345fb19fe9e 100644
--- a/src/lib/char.rs
+++ b/src/lib/char.rs
@@ -93,3 +93,12 @@ pure fn is_whitespace(c: char) -> bool {
         true
     } else if c == ch_no_break_space { true } else { false }
 }
+
+pure fn to_digit(c: char) -> u8 {
+    alt c {
+        '0' to '9' { c as u8 - ('0' as u8) }
+        'a' to 'z' { c as u8 + 10u8 - ('a' as u8) }
+        'A' to 'Z' { c as u8 + 10u8 - ('A' as u8) }
+        _ { fail; }
+    }
+}
diff --git a/src/lib/int.rs b/src/lib/int.rs
index 41d166fe3fc14..62fb0a7cb63ae 100644
--- a/src/lib/int.rs
+++ b/src/lib/int.rs
@@ -112,7 +112,11 @@ fn parse_buf(buf: [u8], radix: uint) -> int {
     }
     let n = 0;
     while true {
-        n += (buf[i] - ('0' as u8) as int) * power;
+        let digit = char::to_digit(buf[i] as char);
+        if (digit as uint) >= radix {
+            fail;
+        }
+        n += (digit as int) * power;
         power *= radix as int;
         if i <= start { ret n; }
         i -= 1u;
diff --git a/src/lib/uint.rs b/src/lib/uint.rs
index cf50b70e1cd8c..5de9bd974e43a 100644
--- a/src/lib/uint.rs
+++ b/src/lib/uint.rs
@@ -100,7 +100,11 @@ fn parse_buf(buf: [u8], radix: uint) -> uint {
     let power = 1u;
     let n = 0u;
     while true {
-        n += (buf[i] - ('0' as u8) as uint) * power;
+        let digit = char::to_digit(buf[i] as char);
+        if (digit as uint) >= radix {
+            fail;
+        }
+        n += (digit as uint) * power;
         power *= radix;
         if i == 0u { ret n; }
         i -= 1u;
diff --git a/src/test/stdtest/char.rs b/src/test/stdtest/char.rs
new file mode 100644
index 0000000000000..b2724ca325d61
--- /dev/null
+++ b/src/test/stdtest/char.rs
@@ -0,0 +1,28 @@
+use std;
+import std::char;
+
+#[test]
+fn test_is_whitespace() {
+    assert char::is_whitespace(' ');
+    assert char::is_whitespace('\u2007');
+    assert char::is_whitespace('\t');
+    assert char::is_whitespace('\n');
+
+    assert !char::is_whitespace('a');
+    assert !char::is_whitespace('_');
+    assert !char::is_whitespace('\u0000');
+}
+
+#[test]
+fn test_to_digit() {
+    assert (char::to_digit('0') == 0u8);
+    assert (char::to_digit('1') == 1u8);
+    assert (char::to_digit('2') == 2u8);
+    assert (char::to_digit('9') == 9u8);
+    assert (char::to_digit('a') == 10u8);
+    assert (char::to_digit('A') == 10u8);
+    assert (char::to_digit('b') == 11u8);
+    assert (char::to_digit('B') == 11u8);
+    assert (char::to_digit('z') == 35u8);
+    assert (char::to_digit('Z') == 35u8);
+}
diff --git a/src/test/stdtest/int.rs b/src/test/stdtest/int.rs
index 282e16daf08a0..1bd67d5c45ecf 100644
--- a/src/test/stdtest/int.rs
+++ b/src/test/stdtest/int.rs
@@ -2,6 +2,7 @@
 use std;
 import std::int;
 import std::str::eq;
+import std::str::bytes;
 
 #[test]
 fn test_from_str() {
@@ -18,6 +19,27 @@ fn test_from_str() {
     assert(int::from_str("-00100") == -100);
 }
 
+#[test]
+fn test_parse_buf() {
+    assert (int::parse_buf(bytes("123"), 10u) == 123);
+    assert (int::parse_buf(bytes("1001"), 2u) == 9);
+    assert (int::parse_buf(bytes("123"), 8u) == 83);
+    assert (int::parse_buf(bytes("123"), 16u) == 291);
+    assert (int::parse_buf(bytes("ffff"), 16u) == 65535);
+    assert (int::parse_buf(bytes("FFFF"), 16u) == 65535);
+    assert (int::parse_buf(bytes("z"), 36u) == 35);
+    assert (int::parse_buf(bytes("Z"), 36u) == 35);
+
+    assert (int::parse_buf(bytes("-123"), 10u) == -123);
+    assert (int::parse_buf(bytes("-1001"), 2u) == -9);
+    assert (int::parse_buf(bytes("-123"), 8u) == -83);
+    assert (int::parse_buf(bytes("-123"), 16u) == -291);
+    assert (int::parse_buf(bytes("-ffff"), 16u) == -65535);
+    assert (int::parse_buf(bytes("-FFFF"), 16u) == -65535);
+    assert (int::parse_buf(bytes("-z"), 36u) == -35);
+    assert (int::parse_buf(bytes("-Z"), 36u) == -35);
+}
+
 #[test]
 fn test_to_str() {
     assert (eq(int::to_str(0, 10u), "0"));
diff --git a/src/test/stdtest/stdtest.rc b/src/test/stdtest/stdtest.rc
index c47b85c65f8a6..501879c540f8a 100644
--- a/src/test/stdtest/stdtest.rc
+++ b/src/test/stdtest/stdtest.rc
@@ -2,6 +2,7 @@ use std;
 
 mod bitv;
 mod box;
+mod char;
 mod comm;
 mod deque;
 mod either;
diff --git a/src/test/stdtest/uint.rs b/src/test/stdtest/uint.rs
index 141b59ace82a8..35bd65c0c057f 100644
--- a/src/test/stdtest/uint.rs
+++ b/src/test/stdtest/uint.rs
@@ -3,6 +3,26 @@
 // -*- rust -*-
 use std;
 import std::uint;
+import std::str::bytes;
+
+#[test]
+fn test_from_str() {
+    assert (uint::from_str("0") == 0u);
+    assert (uint::from_str("3") == 3u);
+    assert (uint::from_str("10") == 10u);
+    assert (uint::from_str("123456789") == 123456789u);
+    assert (uint::from_str("00100") == 100u);
+}
+
+#[test]
+fn test_parse_buf() {
+    assert (uint::parse_buf(bytes("123"), 10u) == 123u);
+    assert (uint::parse_buf(bytes("1001"), 2u) == 9u);
+    assert (uint::parse_buf(bytes("123"), 8u) == 83u);
+    assert (uint::parse_buf(bytes("123"), 16u) == 291u);
+    assert (uint::parse_buf(bytes("ffff"), 16u) == 65535u);
+    assert (uint::parse_buf(bytes("z"), 36u) == 35u);
+}
 
 #[test]
 fn test_next_power_of_two() {
@@ -53,4 +73,4 @@ fn test_overflows() {
    assert (uint::max_value() > 0u);
    assert (uint::min_value() <= 0u);
    assert (uint::min_value() + uint::max_value() + 1u == 0u);
-}
\ No newline at end of file
+}