diff --git a/Database/MongoDB/BSON.hs b/Database/MongoDB/BSON.hs
index 5a5c5c3..eca1007 100644
--- a/Database/MongoDB/BSON.hs
+++ b/Database/MongoDB/BSON.hs
@@ -114,10 +114,10 @@ toDataType (-1) = DataMinKey
 toDataType 127 = DataMaxKey
 toDataType d = toEnum d
 
-fromDataType :: DataType -> Int
+fromDataType :: DataType -> Int8
 fromDataType DataMinKey = - 1
 fromDataType DataMaxKey = 127
-fromDataType d = fromEnum d
+fromDataType d = fromIntegral $ fromEnum d
 
 data BinarySubType =
     BSTUNDEFINED1      |
@@ -133,9 +133,9 @@ toBinarySubType :: Int -> BinarySubType
 toBinarySubType 0x80 = BSTUserDefined
 toBinarySubType d = toEnum d
 
-fromBinarySubType :: BinarySubType -> Int
+fromBinarySubType :: BinarySubType -> Int8
 fromBinarySubType BSTUserDefined = 0x80
-fromBinarySubType d = fromEnum d
+fromBinarySubType d = fromIntegral $ fromEnum d
 
 getBsonDoc :: Get BsonDoc
 getBsonDoc = liftM snd getDoc
@@ -261,8 +261,8 @@ putVal (BsonBinary t bs)= do putI32 $ fromIntegral $ 4 + L.length bs
                              putLazyByteString bs
 putVal BsonUndefined    = putNothing
 putVal (BsonObjectId o) = putLazyByteString o
-putVal (BsonBool False) = putI8 (0::Int)
-putVal (BsonBool True)  = putI8 (1::Int)
+putVal (BsonBool False) = putI8 0
+putVal (BsonBool True)  = putI8 1
 putVal (BsonDate pt)    = putI64 $ round $ 1000 * (realToFrac pt :: Double)
 putVal BsonNull         = putNothing
 putVal (BsonRegex r opt)= do putS r
diff --git a/Database/MongoDB/Util.hs b/Database/MongoDB/Util.hs
index a187cab..6c3c6b9 100644
--- a/Database/MongoDB/Util.hs
+++ b/Database/MongoDB/Util.hs
@@ -58,7 +58,7 @@ getS = getLazyByteStringNul >>= \s -> return (fromIntegral $ L.length s + 1, s)
 getNull :: Get ()
 getNull = do {c <- getC; assert (c == '\0') $ return ()}
 
-putI8 :: (Integral i) => i -> Put
+putI8 :: Int8 -> Put
 putI8 = putWord8 . fromIntegral
 
 putI32 :: Int32 -> Put
@@ -71,7 +71,7 @@ putNothing :: Put
 putNothing = putByteString $ pack ""
 
 putNull :: Put
-putNull = putI8 (0::Int)
+putNull = putI8 0
 
 putS :: L8.ByteString -> Put
 putS s = putLazyByteString s >> putNull