diff --git a/src/Database/PostgreSQL/LibPQ.hsc b/src/Database/PostgreSQL/LibPQ.hsc
index 8699b56..0b5186e 100644
--- a/src/Database/PostgreSQL/LibPQ.hsc
+++ b/src/Database/PostgreSQL/LibPQ.hsc
@@ -754,15 +754,12 @@ 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 (intToCInt n) ts vs ls fs
   where
     AccumParams oids values c_lengths formats =
         foldr accum (AccumParams [] [] [] []) params
 
-    n :: CInt
-    !n = intToCInt $ length params
-
     accum :: Maybe (Oid, B.ByteString, Format) -> AccumParams -> AccumParams
     accum Nothing ~(AccumParams a b c d) =
         AccumParams (invalidOid : a) (Nothing : b) (0 : c) (0 : d)
@@ -790,15 +787,12 @@ 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 (intToCInt n) vs ls fs
   where
     AccumPrepParams values c_lengths formats =
         foldr accum (AccumPrepParams [] [] []) params
 
-    n :: CInt
-    n = intToCInt $ length params
-
     accum :: Maybe (B.ByteString ,Format) -> AccumPrepParams -> AccumPrepParams
     accum Nothing ~(AccumPrepParams a b c) =
         AccumPrepParams (Nothing : a) (0 : b) (0 : c)