diff --git a/src/libcore/fmt/num.rs b/src/libcore/fmt/num.rs
index c8218172583d6..ee989854a3772 100644
--- a/src/libcore/fmt/num.rs
+++ b/src/libcore/fmt/num.rs
@@ -134,7 +134,7 @@ macro_rules! radix {
     }
 }
 
-radix! { Binary,    2, "0b", x @  0 ...  2 => b'0' + x }
+radix! { Binary,    2, "0b", x @  0 ...  1 => b'0' + x }
 radix! { Octal,     8, "0o", x @  0 ...  7 => b'0' + x }
 radix! { Decimal,  10, "",   x @  0 ...  9 => b'0' + x }
 radix! { LowerHex, 16, "0x", x @  0 ...  9 => b'0' + x,