diff --git a/src/gmser_dyn.erl b/src/gmser_dyn.erl
index 1acb533..08511c4 100644
--- a/src/gmser_dyn.erl
+++ b/src/gmser_dyn.erl
@@ -26,6 +26,7 @@
 %% register a type schema, inspect existing schema
 -export([ register_types/1
         , registered_types/0
+        , registered_types/1
         , latest_vsn/0
         , get_opts/1
         , set_opts/1
@@ -52,50 +53,54 @@
 
 serialize(Term) ->
     Vsn = latest_vsn(),
-    rlp_encode(encode_(Term, Vsn, registered_types(Vsn))).
+    rlp_encode(encode(Term, Vsn, registered_types(Vsn))).
 
-serialize(Term, Types) ->
+serialize(Term, Types0) ->
+    Types = proper_types(Types0),
     Vsn = types_vsn(Types),
-    rlp_encode(encode_(Term, Vsn, Types)).
+    rlp_encode(encode(Term, Vsn, Types)).
 
 serialize(Term, Vsn, Types) ->
-    rlp_encode(encode_(Term, Vsn, Types)).
+    rlp_encode(encode(Term, Vsn, proper_types(Types, Vsn))).
 
 serialize_typed(Type, Term) ->
     Vsn = latest_vsn(),
-    rlp_encode(encode_typed_(Type, Term, Vsn, registered_types(Vsn))).
+    rlp_encode(encode_typed(Type, Term, Vsn, registered_types(Vsn))).
 
-serialize_typed(Type, Term, Types) ->
+serialize_typed(Type, Term, Types0) ->
+    Types = proper_types(Types0),
     Vsn = types_vsn(Types),
-    rlp_encode(encode_typed_(Type, Term, Vsn, Types)).
+    rlp_encode(encode_typed(Type, Term, Vsn, Types)).
 
 serialize_typed(Type, Term, Vsn, Types) ->
-    rlp_encode(encode_typed_(Type, Term, Vsn, Types)).
+    rlp_encode(encode_typed(Type, Term, Vsn, proper_types(Types, Vsn))).
 
 deserialize(Binary) ->
     Fields0 = rlp_decode(Binary),
     case decode_tag_and_vsn(Fields0) of
         {0, Vsn, Fields} ->
-            decode(Fields, Vsn, registered_types(Vsn));
+            decode_(Fields, Vsn, registered_types(Vsn));
         Other ->
             error({illegal_serialization, Other})
     end.
 
-deserialize(Binary, Types) ->
-    Vsn0 = maps:get(vsn, Types, undefined),
+deserialize(Binary, Types0) ->
+    Types = proper_types(Types0),
+    Vsn0 = types_vsn(Types),
     Fields0 = rlp_decode(Binary),
     case decode_tag_and_vsn(Fields0) of
         {0, Vsn, Fields} when Vsn0 == undefined; Vsn0 == Vsn ->
-            decode(Fields, Vsn, Types);
+            decode_(Fields, Vsn, Types);
         Other ->
             error({illegal_serialization, Other})
     end.
             
-deserialize(Binary, Vsn, Types) ->
+deserialize(Binary, Vsn, Types0) ->
+    Types = proper_types(Types0),
     Fields0 = rlp_decode(Binary),
     case decode_tag_and_vsn(Fields0) of
         {0, Vsn, Fields} ->
-            decode(Fields, Vsn, Types);
+            decode_(Fields, Vsn, Types);
         Other ->
             error({illegal_serialization, Other})
     end.
@@ -104,11 +109,12 @@ encode(Term) ->
     Vsn = latest_vsn(),
     encode(Term, Vsn, registered_types(Vsn)).
 
-encode(Term, Types) ->
+encode(Term, Types0) ->
+    Types = proper_types(Types0),
     encode(Term, types_vsn(Types), Types).
 
 encode(Term, Vsn, Types0) ->
-    Types = assert_vsn(Vsn, Types0),
+    Types = proper_types(Types0, Vsn),
     [ encode_basic(int, 0)
     , encode_basic(int, Vsn)
     , encode_(Term, Vsn, Types) ].
@@ -117,11 +123,12 @@ encode_typed(Type, Term) ->
     Vsn = latest_vsn(),
     encode_typed(Type, Term, Vsn, registered_types(Vsn)).
 
-encode_typed(Type, Term, Types) ->
+encode_typed(Type, Term, Types0) ->
+    Types = proper_types(Types0),
     encode_typed(Type, Term, types_vsn(Types), Types).
 
 encode_typed(Type, Term, Vsn, Types0) ->
-    Types = assert_vsn(Vsn, Types0),
+    Types = proper_types(Types0, Vsn),
     [ encode_basic(int, 0)
     , encode_basic(int, Vsn)
     , encode_typed_(Type, Term, Vsn, Types) ].
@@ -130,11 +137,12 @@ decode(Fields) ->
     Vsn = latest_vsn(),
     decode(Fields, Vsn, registered_types(Vsn)).
 
-decode(Fields, Types) ->
+decode(Fields, Types0) ->
+    Types = proper_types(Types0),
     decode(Fields, types_vsn(Types), Types).
 
 decode(Fields0, Vsn, Types0) ->
-    Types = assert_vsn(Vsn, Types0),
+    Types = proper_types(Types0, Vsn),
     case decode_tag_and_vsn(Fields0) of
         {0, Vsn, Fields} ->
             decode_(Fields, Vsn, Types);
@@ -146,11 +154,12 @@ decode_typed(Type, Fields) ->
     Vsn = latest_vsn(),
     decode_typed(Type, Fields, Vsn, registered_types(Vsn)).
 
-decode_typed(Type, Fields, Types) ->
+decode_typed(Type, Fields, Types0) ->
+    Types = proper_types(Types0),
     decode_typed(Type, Fields, types_vsn(Types), Types).
 
 decode_typed(Type, Fields0, Vsn, Types0) ->
-    Types = assert_vsn(Vsn, Types0),
+    Types = proper_types(Types0, Vsn),
     case decode_tag_and_vsn(Fields0) of
         {0, Vsn, Fields} ->
             decode_from_template(Type, Fields, Vsn, Types);
@@ -163,6 +172,16 @@ decode_tag_and_vsn([TagBin, VsnBin, Fields]) ->
      decode_basic(int, VsnBin),
      Fields}.
 
+proper_types(undefined) ->
+    registered_types(latest_vsn());
+proper_types(#{} = Types) ->
+    Types.
+
+proper_types(undefined, Vsn) ->
+    registered_types(Vsn);
+proper_types(#{} = Types, Vsn) ->
+    assert_vsn(Vsn, Types).
+
 types_vsn(#{vsn := Vsn}) -> Vsn;
 types_vsn(_) -> latest_vsn().
 
@@ -768,6 +787,11 @@ round_trip_test_() ->
         T <- t_sample_types()
     ].
 
+ser_round_trip_test_() ->
+    [?_test(t_ser_round_trip(T)) ||
+        T <- t_sample_types()
+    ].
+
 t_sample_types() ->
     [ 5
     , -5
@@ -813,6 +837,11 @@ t_round_trip(T) ->
     ?debugVal(T),
     ?assertMatch({T, T}, {T, decode(encode(T))}).
 
+t_ser_round_trip(T) ->
+    Data = serialize(T),
+    ?debugFmt("Data (~p) = ~p~n", [T, Data]),
+    ?assertMatch({T, T}, {T, deserialize(Data)}).
+
 t_round_trip_typed(Type, T) ->
     ?debugVal(T),
     ?assertMatch({T, T}, {T, decode(encode_typed(Type, T))}).