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:               0.2.7
+version:               0.2.8
 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
@@ -272,8 +272,8 @@
 -- See DF012, pg. 3-16 of the RTCM3 spec
 toL_L1 :: GpsL1Observation -> GpsL1ExtObservation -> CarrierPhase
 toL_L1 l1 l1e = CarrierPhase
-  { _carrierPhase_i = fromIntegral li
-  , _carrierPhase_f = fromIntegral lf
+  { _carrierPhase_i = fromIntegral li'
+  , _carrierPhase_f = fromIntegral lf'
   } where
     p = metricPseudorange l1 l1e
     -- Convert to SBP carrier phase representation per
@@ -283,9 +283,12 @@
     l = lm / (lightSpeedMS / l1frequency)
     li :: Int32
     li = floor l
-    lf :: Word8
+    lf :: Word16
     lf = round ((l - fromIntegral li) * q32Width)
-
+    li' :: Int32
+    li' = if lf == 256 then li + 1 else li
+    lf' :: Word8
+    lf' = if lf == 256 then 0 else fromIntegral lf
 -- | Construct SBP L2 GPS carrier phase from L2 RTCM observation
 --
 -- See DF018, pg. 3-18 of the RTCM3 spec