diff --git a/gnss-converters.cabal b/gnss-converters.cabal
--- a/gnss-converters.cabal
+++ b/gnss-converters.cabal
@@ -1,5 +1,5 @@
 name:                  gnss-converters
-version:               0.1.19
+version:               0.1.20
 synopsis:              GNSS Converters.
 description:           Haskell bindings for GNSS converters.
 homepage:              http://github.com/swift-nav/gnss-converters
diff --git a/src/Data/RTCM3/SBP.hs b/src/Data/RTCM3/SBP.hs
--- a/src/Data/RTCM3/SBP.hs
+++ b/src/Data/RTCM3/SBP.hs
@@ -418,10 +418,10 @@
     , _msgObsDepC_obs    = packed
     }
 
--- | Sender Id is Station Id with high byte or'd in
+-- | 16 bit SBP Sender Id is 12 bit RTCM Station Id with high nibble or'd in
 --
 toSender :: Word16 -> Word16
-toSender = (.|. 0xf00)
+toSender = (.|. 0xf000)
 
 
 --------------------------------------------------------------------------------
@@ -543,4 +543,3 @@
   day <- utctDay <$> getCurrentTime
   let wn = fromIntegral $ div (diffDays day (fromGregorian 1980 1 6)) 7
   Store <$> newIORef wn <*> newIORef mempty <*> newIORef mempty
-