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: 0.3.23
+version: 0.3.24
 cabal-version: >=1.22
 build-type: Simple
 license: BSD3
@@ -37,7 +37,7 @@
         monad-control >=1.0.1.0,
         mtl >=2.2.1,
         resourcet >=1.1.9,
-        rtcm >=0.2.10,
+        rtcm >=0.2.11,
         sbp >=2.3.1,
         time >=1.5.0.1,
         transformers-base >=0.4.4,
diff --git a/src/Data/RTCM3/SBP/Biases.hs b/src/Data/RTCM3/SBP/Biases.hs
--- a/src/Data/RTCM3/SBP/Biases.hs
+++ b/src/Data/RTCM3/SBP/Biases.hs
@@ -14,19 +14,31 @@
   ( converter
   ) where
 
-import BasicPrelude
+import BasicPrelude hiding (mask)
 import Control.Lens
 import Data.Bits
 import Data.Conduit
+import Data.Int
 import Data.RTCM3
 import Data.Word
 import SwiftNav.SBP
 
+{-# ANN module ("HLint: ignore Use head"::String) #-}
+
 -- | Derive sender from station.
 --
 toSender :: Word16 -> Word16
 toSender station = station .|. 61440
 
+-- | Expand out array of biases.
+--
+toBiases :: Word8 -> Int -> [Int16] -> [Int16]
+toBiases mask i (bias:biases)
+  | testBit mask i = bias : toBiases mask (i+1) biases
+toBiases mask i biases
+  | null biases = biases
+  | otherwise = 0 : toBiases mask (i+1) biases
+
 -- | Convert an RTCM 1230 GLO biases message into an SBP MsgGloBiases.
 --
 converter :: Monad m => Msg1230 -> Conduit i m [SBPMsg]
@@ -34,11 +46,12 @@
   let bias   = m ^. msg1230_bias
       sender = toSender $ bias ^. glonassBias_station
       scale  = bool 50 (-50) $ bias ^. glonassBias_bias
+      biases = toBiases (bias ^. glonassBias_mask) 0 (bias ^. glonassBias_biases) <> repeat 0
       m'     = MsgGloBiases
         { _msgGloBiases_mask      = bias ^. glonassBias_mask
-        , _msgGloBiases_l1ca_bias = scale * bias ^. glonassBias_l1ca
-        , _msgGloBiases_l1p_bias  = scale * bias ^. glonassBias_l1p
-        , _msgGloBiases_l2ca_bias = scale * bias ^. glonassBias_l2ca
-        , _msgGloBiases_l2p_bias  = scale * bias ^. glonassBias_l2p
+        , _msgGloBiases_l1ca_bias = scale * biases !! 0
+        , _msgGloBiases_l1p_bias  = scale * biases !! 1
+        , _msgGloBiases_l2ca_bias = scale * biases !! 2
+        , _msgGloBiases_l2p_bias  = scale * biases !! 3
         }
   yield [SBPMsgGloBiases m' $ toSBP m' sender]