diff --git a/src/Database/PostgreSQL/LibPQ.hsc b/src/Database/PostgreSQL/LibPQ.hsc
index 3f8a00d..2ab9f25 100644
--- a/src/Database/PostgreSQL/LibPQ.hsc
+++ b/src/Database/PostgreSQL/LibPQ.hsc
@@ -756,13 +756,11 @@ withParams params action =
         withMany (maybeWith B.useAsCString) values $ \c_values ->
             withArray c_values $ \vs ->
                 withArray c_lengths $ \ls ->
-                    withArray formats $ \fs ->
-                        action n ts vs ls fs
+                    withArrayLen formats $ \n fs ->
+                        action (toEnum n) ts vs ls fs
   where
-    (oids, values, lengths, formats) =
+    (oids, values, c_lengths, formats) =
         foldl' accum ([],[],[],[]) $ reverse params
-    !c_lengths = map toEnum lengths :: [CInt]
-    !n = toEnum $ length params
 
     accum (!a,!b,!c,!d) Nothing = ( invalidOid:a
                                   , Nothing:b
@@ -771,7 +769,7 @@ withParams params action =
                                   )
     accum (!a,!b,!c,!d) (Just (t,v,f)) = ( t:a
                                          , (Just v):b
-                                         , (B.length v):c
+                                         , (toEnum $ B.length v):c
                                          , (toEnum $ fromEnum f):d
                                          )
 
@@ -784,19 +782,17 @@ withParamsPrepared params action =
     withMany (maybeWith B.useAsCString) values $ \c_values ->
         withArray c_values $ \vs ->
             withArray c_lengths $ \ls ->
-                withArray formats $ \fs ->
-                    action n vs ls fs
+                withArrayLen formats $ \n fs ->
+                    action (toEnum n) vs ls fs
   where
-    (values, lengths, formats) = foldl' accum ([],[],[]) $ reverse params
-    !c_lengths = map toEnum lengths :: [CInt]
-    !n = toEnum $ length params
+    (values, c_lengths, formats) = foldl' accum ([],[],[]) $ reverse params
 
     accum (!a,!b,!c) Nothing       = ( Nothing:a
                                      , 0:b
                                      , 0:c
                                      )
     accum (!a,!b,!c) (Just (v, f)) = ( (Just v):a
-                                     , (B.length v):b
+                                     , (toEnum $ B.length v):b
                                      , (toEnum $ fromEnum f):c
                                      )