diff --git a/Statistics/Distribution/Poisson.hs b/Statistics/Distribution/Poisson.hs
--- a/Statistics/Distribution/Poisson.hs
+++ b/Statistics/Distribution/Poisson.hs
@@ -55,7 +55,7 @@
     | l >= 3 && x >= l * 100  = 0
     | x >= max 1 l * 200      = 0
     | l < 20 && x <= 100      = exp (-l) * l ** x / factorial (floor x)
-    | otherwise               = x * log l - logGamma (x + 1) - l
+    | otherwise               = exp (x * log l - logGamma (x + 1) - l)
 {-# INLINE density #-}
 
 cumulative :: PoissonDistribution -> Double -> Double
diff --git a/statistics.cabal b/statistics.cabal
--- a/statistics.cabal
+++ b/statistics.cabal
@@ -1,5 +1,5 @@
 name:           statistics
-version:        0.5.1.1
+version:        0.5.1.2
 synopsis:       A library of statistical types, data, and functions
 description:
   This library provides a number of common functions and types useful