diff --git a/hsyslog-udp.cabal b/hsyslog-udp.cabal
--- a/hsyslog-udp.cabal
+++ b/hsyslog-udp.cabal
@@ -1,5 +1,5 @@
 name:                   hsyslog-udp
-version:                0.1.2
+version:                0.2.0
 synopsis:               Log to syslog over a network via UDP
 description:            Supports <https://tools.ietf.org/html/rfc5424 RFC 5424>,
                         <https://tools.ietf.org/html/rfc3164 RFC 3164>, or any
@@ -26,12 +26,12 @@
   exposed-modules:      System.Posix.Syslog.UDP
 
   Build-Depends:        base >= 3 && < 5
-                      , bytestring == 0.10.*
-                      , hsyslog == 4.*
-                      , network == 2.6.*
-                      , text == 1.2.*
-                      , time < 1.7
-                      , unix == 2.7.*
+                      , bytestring < 0.11
+                      , hsyslog >= 5 && < 6
+                      , network < 2.7
+                      , text < 1.3
+                      , time < 1.9
+                      , unix < 2.8
 
 test-suite specs
   default-language:     Haskell2010
@@ -41,6 +41,6 @@
   other-modules:        System.Posix.Syslog.UDPSpec
 
   Build-Depends:        base >= 3 && < 5
-                      , hspec == 2.2.*
+                      , hspec < 2.5
                       , hsyslog-udp
-                      , time < 1.7
+                      , time < 1.9
diff --git a/src/System/Posix/Syslog/UDP.hs b/src/System/Posix/Syslog/UDP.hs
--- a/src/System/Posix/Syslog/UDP.hs
+++ b/src/System/Posix/Syslog/UDP.hs
@@ -23,7 +23,6 @@
     -- ** Re-exports from <http://hackage.haskell.org/package/hsyslog hsyslog>
     L.Priority (..)
   , L.Facility (..)
-  , L.PriorityMask (..)
     -- ** Newtypes for various String/Int values
     -- | Refer to
     -- <https://tools.ietf.org/html/rfc5424#section-6.2 RFC 5424 section 6.2>
@@ -67,7 +66,7 @@
 
 import Control.Exception (SomeException, catch)
 import Control.Monad (void)
-import Data.Bits ((.&.))
+import Data.Bits ((.|.))
 import Data.ByteString (ByteString)
 import Data.Monoid ((<>))
 import Data.Text (Text)
@@ -84,9 +83,11 @@
 import qualified Network.Socket.ByteString as SB
 import qualified System.Posix.Process as P
 import qualified System.Posix.Syslog as L
+import System.Posix.Syslog.Facility (fromFacility)
+import System.Posix.Syslog.Priority (fromPriority)
 
 type Severity = L.Priority
-type SeverityMask = L.PriorityMask
+type SeverityMask = [L.Priority]
 
 type Protocol
   =  PriVal
@@ -197,7 +198,7 @@
     processId <- getProcessId
     return SyslogConfig {..}
   where
-    severityMask = L.NoMask
+    severityMask = [minBound..maxBound]
     address = localhost
     protocol = rfc3164Protocol
 
@@ -369,12 +370,12 @@
   -> Severity
   -> Maybe PriVal
 maskedPriVal mask fac sev
-    | mask == L.NoMask = prival
     | masked = Nothing
     | otherwise = prival
   where
-    prival = Just . PriVal $ L.makePri fac sev
-    masked = L._LOG_MASK (L.fromPriority sev) .&. L.fromPriorityMask mask == 0
+    priority = fromFacility fac .|. fromPriority sev
+    prival = Just $ PriVal priority
+    masked = not $ sev `elem` mask
 
 -- internal functions
 
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -14,7 +14,7 @@
 logMessages :: IO ()
 logMessages = do
     syslog <- defaultConfig >>= initSyslog
-    syslog USER Debug "hello thar!"
+    syslog User Debug "hello thar!"
 
 runSpecs :: IO ()
 runSpecs =
diff --git a/test/System/Posix/Syslog/UDPSpec.hs b/test/System/Posix/Syslog/UDPSpec.hs
--- a/test/System/Posix/Syslog/UDPSpec.hs
+++ b/test/System/Posix/Syslog/UDPSpec.hs
@@ -10,17 +10,19 @@
 
 spec :: Spec
 spec = do
+  let upTo x = [minBound..x]
+      noMask = [minBound..maxBound]
   describe "maskedPriVal" $ do
     it "returns a Just if priorities remain after masking" $
-      let result = maskedPriVal (UpTo Debug) LOCAL4 Notice
+      let result = maskedPriVal (upTo Debug) Local4 Notice
       in result `shouldBe` Just (PriVal 165)
 
     it "returns Nothing if all priorities are masked" $
-      let result = maskedPriVal (UpTo Info) USER Debug
+      let result = maskedPriVal (upTo Info) User Debug
       in result `shouldBe` Nothing
 
   describe "rfc5424Packet" $ do
-    let (Just priVal) = maskedPriVal NoMask USER Debug
+    let (Just priVal) = maskedPriVal noMask User Debug
 
     it "uses the NILVALUE for Nothing values" $
       let
@@ -56,7 +58,7 @@
 
   describe "rfc3164Packet" $ do
     let
-      (Just priVal) = maskedPriVal NoMask USER Debug
+      (Just priVal) = maskedPriVal noMask User Debug
       (Just time) = parseTimeM True defaultTimeLocale "%FT%X%QZ" "2003-10-11T22:14:15.003Z" :: Maybe UTCTime
 
     it "correctly formats the message" $
@@ -68,7 +70,7 @@
 
   describe "rsyslogPacket" $ do
     let
-      (Just priVal) = maskedPriVal NoMask USER Debug
+      (Just priVal) = maskedPriVal noMask User Debug
       (Just time) = parseTimeM True defaultTimeLocale "%FT%X%QZ" "2003-10-11T22:14:15.003Z" :: Maybe UTCTime
 
     it "correctly formats the message" $