diff --git a/hoogle.cabal b/hoogle.cabal
--- a/hoogle.cabal
+++ b/hoogle.cabal
@@ -1,7 +1,7 @@
 cabal-version:      >= 1.10
 build-type:         Simple
 name:               hoogle
-version:            4.2.17
+version:            4.2.18
 license:            BSD3
 license-file:       docs/LICENSE
 category:           Development
@@ -40,7 +40,7 @@
         array, containers, directory, filepath, process, random,
         safe,
         binary,
-        bytestring >= 0.10,
+        bytestring >= 0.9,
         conduit >= 0.2,
         parsec >= 2.1,
         deepseq >= 1.1,
diff --git a/src/Hoogle/DataBase/SubstrSearch.hs b/src/Hoogle/DataBase/SubstrSearch.hs
--- a/src/Hoogle/DataBase/SubstrSearch.hs
+++ b/src/Hoogle/DataBase/SubstrSearch.hs
@@ -69,7 +69,7 @@
     deriving Typeable
 
 instance NFData a => NFData (SubstrSearch a) where
-    rnf (SubstrSearch a b c) = rnf (a,b,c)
+    rnf (SubstrSearch a b c) = rnf (a `seq` (),b `seq` (),c)
 
 -- | Create a substring search index. Values are returned in order where possible.
 createSubstrSearch :: [(String,a)] -> SubstrSearch a