diff --git a/Data/Aeson/Encode.hs b/Data/Aeson/Encode.hs
--- a/Data/Aeson/Encode.hs
+++ b/Data/Aeson/Encode.hs
@@ -71,7 +71,7 @@
 fromNumber :: Number -> Builder
 fromNumber (I i) = integral i
 fromNumber (D d)
-    | isNaN d || isInfinite d = "null"
+    | isNaN d || isInfinite d = fromByteString "null"
     | otherwise               = double d
 
 -- | Efficiently serialize a JSON value as a lazy 'L.ByteString'.
diff --git a/aeson.cabal b/aeson.cabal
--- a/aeson.cabal
+++ b/aeson.cabal
@@ -1,5 +1,5 @@
 name:            aeson
-version:         0.3.2.10
+version:         0.3.2.11
 license:         BSD3
 license-file:    LICENSE
 category:        Text, Web, JSON