diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,11 @@
+0.5.1.1
+-------
+* Misc `doctest` fixes.
+
+0.5.1
+-----
+* Added `interval` to facilitate the construction of known non-empty intervals.
+
 0.5
 ---
 * The default `Numeric.Interval` now deals more conventionally with empty intervals.
diff --git a/intervals.cabal b/intervals.cabal
--- a/intervals.cabal
+++ b/intervals.cabal
@@ -1,5 +1,5 @@
 name:              intervals
-version:           0.5.1
+version:           0.5.1.1
 synopsis:          Interval Arithmetic
 description:
   A 'Numeric.Interval.Interval' is a closed, convex set of floating point values.
diff --git a/src/Numeric/Interval/Internal.hs b/src/Numeric/Interval/Internal.hs
--- a/src/Numeric/Interval/Internal.hs
+++ b/src/Numeric/Interval/Internal.hs
@@ -115,7 +115,7 @@
 --
 -- >>> empty
 -- Empty
-empty :: Fractional a => Interval a
+empty :: Ord a => Interval a
 empty = Empty
 {-# INLINE empty #-}
 
@@ -144,8 +144,8 @@
 
 -- | The infinumum (lower bound) of an interval
 --
--- >>> inf (1 ... 20)
--- 1
+-- >>> inf (1.0 ... 20.0)
+-- 1.0
 inf :: Fractional a => Interval a -> a
 inf (I a _) = a
 inf Empty = nan
@@ -153,8 +153,8 @@
 
 -- | The supremum (upper bound) of an interval
 --
--- >>> sup (1 ... 20)
--- 20
+-- >>> sup (1.0 ... 20.0)
+-- 20.0
 sup :: Fractional a => Interval a -> a
 sup (I _ b) = b
 sup Empty = nan
@@ -271,8 +271,8 @@
 -- >>> bisect (singleton 5.0)
 -- (5.0 ... 5.0,5.0 ... 5.0)
 --
--- >>> bisect empty
--- (NaN ... NaN,NaN ... NaN)
+-- >>> bisect Empty
+-- (Empty,Empty)
 bisect :: Fractional a => Interval a -> (Interval a, Interval a)
 bisect Empty = (Empty,Empty)
 bisect (I a b) = (I a m, I m b) where m = a + (b - a) / 2