diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # spherical
 
+## 0.1.2.1
+
+  * Fix `sinc`
+
 ## 0.1.2.0
 
   * Expose `bonne` projection
diff --git a/spherical.cabal b/spherical.cabal
--- a/spherical.cabal
+++ b/spherical.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.18
 name: spherical
-version: 0.1.2.0
+version: 0.1.2.1
 license: BSD3
 license-file: LICENSE
 copyright: Copyright: (c) 2018 Vanessa McHale
diff --git a/src/Math/Geometry/Spherical.hs b/src/Math/Geometry/Spherical.hs
--- a/src/Math/Geometry/Spherical.hs
+++ b/src/Math/Geometry/Spherical.hs
@@ -35,7 +35,8 @@
 toRadians :: Floating a => (a, a) -> (a, a)
 toRadians = both radians
 
-sinc :: Floating a => a -> a
+sinc :: (Eq a, Floating a) => a -> a
+sinc 0 = 1
 sinc x = sin x / x
 
 -- | For use as a reference point
@@ -62,7 +63,7 @@
             | otherwise = (long - referenceLong) / sin (long - referenceLong) * expr
 
 -- | Winkel Tripel projection
-winkel3 :: Floating a => (a, a) -> (a, a)
+winkel3 :: (Eq a, Floating a) => (a, a) -> (a, a)
 winkel3 (long, lat) = ((lambda * cos phi1 + (2 * cos lat * sin (lambda/2)/sinc alpha))/2, (lat + sin lat/sinc alpha)/2)
     where lambda = long - lambda0
           phi1 = acos $ 2 / pi