diff --git a/mu-protobuf.cabal b/mu-protobuf.cabal
--- a/mu-protobuf.cabal
+++ b/mu-protobuf.cabal
@@ -1,5 +1,5 @@
 name:          mu-protobuf
-version:       0.4.1.0
+version:       0.4.2.0
 synopsis:
   Protocol Buffers serialization and gRPC schema import for Mu microservices
 
diff --git a/src/Mu/Adapter/ProtoBuf.hs b/src/Mu/Adapter/ProtoBuf.hs
--- a/src/Mu/Adapter/ProtoBuf.hs
+++ b/src/Mu/Adapter/ProtoBuf.hs
@@ -205,6 +205,7 @@
 
 -- Embedded terms
 class ProtoBridgeEmbedTerm (sch :: Schema tn fn) (t :: TypeDef tn fn) where
+  embedDefaultOneFieldValue :: Maybe (Term sch t)
   termToEmbedProto :: FieldNumber -> Term sch t -> PBEnc.MessageBuilder
   embedProtoToOneFieldValue :: PBDec.Parser PBDec.RawPrimitive (Term sch t)
   -- support for packed encodings
@@ -257,6 +258,7 @@
 
 instance ProtoBridgeTerm sch ('DRecord name args)
          => ProtoBridgeEmbedTerm sch ('DRecord name args) where
+  embedDefaultOneFieldValue = Nothing
   termToEmbedProto fid v = PBEnc.embedded fid (termToProto v)
   embedProtoToOneFieldValue = PBDec.embedded' (protoToTerm @_ @_ @sch @('DRecord name args))
   supportsPackingTerm _ = False
@@ -271,8 +273,10 @@
   termToProto = error "protobuf requires wrapping enums in a message"
   protoToTerm = error "protobuf requires wrapping enums in a message"
 
-instance ProtoBridgeEnum sch name choices
+instance ( ProtoBridgeEnum sch name choices
+         , FindZeroEnum sch name choices )
          => ProtoBridgeEmbedTerm sch ('DEnum name choices) where
+  embedDefaultOneFieldValue = Just $ TEnum $ findZeroEnum @_ @_ @sch @name @choices
   termToEmbedProto fid (TEnum v) = PBEnc.int32 fid (enumToProto @_ @_ @sch @name v)
   embedProtoToOneFieldValue = PBDec.int32 >>= fmap TEnum . protoToEnum @_ @_ @sch @name
   supportsPackingTerm _ = True
@@ -296,6 +300,27 @@
     | otherwise      = S <$> protoToEnum @_ @_ @sch @ty n
     where enumValue = fromIntegral (natVal (Proxy @(FindProtoBufId sch ty c)))
 
+class FindZeroEnum (sch :: Schema tn fn) (ty :: tn) (choices :: [ChoiceDef fn]) where
+  findZeroEnum :: NS Proxy choices
+class FindZeroEnum_ (sch :: Schema tn fn) (ty :: tn) (thisChoice :: ChoiceDef fn) (pbId :: Nat) (restOfChoices :: [ChoiceDef fn]) where
+  findZeroEnum_ :: NS Proxy (thisChoice ': restOfChoices)
+
+instance TypeError ('Text "could not find value 0 for enum")
+         => FindZeroEnum sch ty '[] where
+  findZeroEnum = error "this should never be called"
+instance (FindZeroEnum_ sch ty ('ChoiceDef this) (FindProtoBufId sch ty this) rest)
+         => FindZeroEnum sch ty ('ChoiceDef this ': rest) where
+  findZeroEnum
+    = findZeroEnum_ @_ @_ @sch @ty @('ChoiceDef this) @(FindProtoBufId sch ty this) @rest
+
+instance {-# OVERLAPPABLE #-}
+         (FindZeroEnum sch ty rest)
+         => FindZeroEnum_ sch ty this n rest where
+  findZeroEnum_ = S (findZeroEnum @_ @_ @sch @ty @rest)
+instance {-# OVERLAPS #-}
+         FindZeroEnum_ sch ty this 0 rest where
+  findZeroEnum_ = Z Proxy
+
 -- SIMPLE
 -- ------
 
@@ -409,7 +434,7 @@
 
 instance ProtoBridgeEmbedTerm sch (sch :/: t)
          => ProtoBridgeOneFieldValue sch ('TSchematic t) where
-  defaultOneFieldValue = Nothing
+  defaultOneFieldValue = FSchematic <$> embedDefaultOneFieldValue
   oneFieldValueToProto fid (FSchematic v) = termToEmbedProto fid v
   protoToOneFieldValue = FSchematic <$> embedProtoToOneFieldValue
   supportsPacking _ = supportsPackingTerm (Proxy @(Term sch (sch :/: t)))
diff --git a/src/Mu/Quasi/ProtoBuf.hs b/src/Mu/Quasi/ProtoBuf.hs
--- a/src/Mu/Quasi/ProtoBuf.hs
+++ b/src/Mu/Quasi/ProtoBuf.hs
@@ -65,8 +65,17 @@
 schemaFromProtoBuf :: P.ProtoBuf -> Q (Type, Type)
 schemaFromProtoBuf P.ProtoBuf {P.types = tys} = do
   let decls = flattenDecls (("", tys) :| []) tys
-  (schTys, anns) <- unzip <$> mapM pbTypeDeclToType decls
+  (schTys, anns) <- unzip <$> mapM (pbTypeDeclToType $ shouldOptional decls) decls
   pure (typesToList schTys, typesToList (concat anns))
+  where
+    shouldOptional :: [P.TypeDeclaration] -> P.TypeName -> Bool
+    shouldOptional [] _ = error "this should never happen"
+    shouldOptional (P.DMessage nm _ _ _ _ : _) this
+      | nm == last this = True
+    shouldOptional (P.DEnum nm _ _ : _) this
+      | nm == last this = False
+    shouldOptional (_ : rest) this
+      = shouldOptional rest this
 
 flattenDecls :: NonEmpty (P.Identifier, [P.TypeDeclaration]) -> [P.TypeDeclaration] -> [P.TypeDeclaration]
 flattenDecls (currentScope :| higherScopes) = concatMap flattenDecl
@@ -113,8 +122,8 @@
         "" -> x
         _  -> fst currentScope <> "." <> x
 
-pbTypeDeclToType :: P.TypeDeclaration -> Q (Type, [Type])
-pbTypeDeclToType (P.DEnum name _ fields) = do
+pbTypeDeclToType :: (P.TypeName -> Bool) -> P.TypeDeclaration -> Q (Type, [Type])
+pbTypeDeclToType _ (P.DEnum name _ fields) = do
   (tys, anns) <- unzip <$> mapM pbChoiceToType fields
   (,) <$> [t|'DEnum $(textToStrLit name) $(pure $ typesToList tys)|] <*> pure anns
   where
@@ -122,7 +131,7 @@
     pbChoiceToType (P.EnumField nm number _)
       = (,) <$> [t|'ChoiceDef $(textToStrLit nm) |]
             <*> [t|'AnnField $(textToStrLit name) $(textToStrLit nm) ('ProtoBufId $(intToLit number) '[]) |]
-pbTypeDeclToType (P.DMessage name _ _ fields _) = do
+pbTypeDeclToType shouldOptional (P.DMessage name _ _ fields _) = do
   (tys, anns) <- unzip <$> mapM pbMsgFieldToType fields
   (,) <$> [t|'DRecord $(textToStrLit name) $(pure $ typesToList tys)|] <*> pure anns
   where
@@ -131,8 +140,12 @@
     -- it's possible to distinguish whether it's missing on wire
     -- or should be set to the default, so use Option
     -- +info -> https://github.com/higherkindness/mu-haskell/pull/130#issuecomment-596433307
-    pbMsgFieldToType (P.NormalField P.Single ty@(P.TOther _) nm n opts) =
+    pbMsgFieldToType (P.NormalField P.Single ty@(P.TOther innerTy) nm n opts)
+        | shouldOptional innerTy =
         (,) <$> [t| 'FieldDef $(textToStrLit nm) ('TOption $(pbFieldTypeToType ty)) |]
+            <*> [t| 'AnnField $(textToStrLit name) $(textToStrLit nm) ('ProtoBufId $(intToLit n) $(typesToList <$> mapM pbOption opts)) |]
+        | otherwise =
+        (,) <$> [t| 'FieldDef $(textToStrLit nm) $(pbFieldTypeToType ty) |]
             <*> [t| 'AnnField $(textToStrLit name) $(textToStrLit nm) ('ProtoBufId $(intToLit n) $(typesToList <$> mapM pbOption opts)) |]
     pbMsgFieldToType (P.NormalField P.Single ty nm n opts) =
         (,) <$> [t| 'FieldDef $(textToStrLit nm) $(pbFieldTypeToType ty) |]
diff --git a/test/ProtoBuf.hs b/test/ProtoBuf.hs
--- a/test/ProtoBuf.hs
+++ b/test/ProtoBuf.hs
@@ -25,7 +25,7 @@
   = MPerson { firstName     :: T.Text
             , lastName      :: T.Text
             , age           :: Maybe Int
-            , gender        :: Maybe Gender
+            , gender        :: Gender
             , address       :: MAddress
             , lucky_numbers :: [Int]
             , things        :: M.Map T.Text Int }
@@ -54,7 +54,7 @@
      , 'AnnField "gender" "gender7" ('ProtoBufId 11 '[])
      , 'AnnField "gender" "gender8" ('ProtoBufId 12 '[])
      , 'AnnField "gender" "gender9" ('ProtoBufId 13 '[])
-     , 'AnnField "gender" "unspecified" ('ProtoBufId 14 '[])
+     , 'AnnField "gender" "unspecified" ('ProtoBufId 0 '[])
      , 'AnnField "address" "postcode" ('ProtoBufId 1 '[])
      , 'AnnField "address" "country"  ('ProtoBufId 2 '[])
      , 'AnnField "person" "firstName" ('ProtoBufId 1 '[])
@@ -70,11 +70,11 @@
 
 examplePerson1, examplePerson2 :: MPerson
 examplePerson1 = MPerson "Haskellio" "Gómez"
-                         (Just 30) (Just Male)
+                         (Just 30) Male
                          exampleAddress [1,2,3]
                          (M.fromList [("pepe", 1), ("juan", 2)])
 examplePerson2 = MPerson "Cuarenta" "Siete"
-                         Nothing Nothing
+                         Nothing Unspecified
                          exampleAddress [] M.empty
 
 main :: IO ()