diff --git a/src/geef_commit.erl b/src/geef_commit.erl
index be6a69b..e85a22e 100644
--- a/src/geef_commit.erl
+++ b/src/geef_commit.erl
@@ -16,6 +16,6 @@ tree(#geef_object{type=commit,handle=Handle}) ->
 	    Other
     end.
 
--spec lookup(pid(), geef_oid() | iolist()) -> geef_object().
+-spec lookup(pid(), geef_oid() | iolist()) -> {ok, geef_object()} | {error, term()}.
 lookup(Repo, Id) ->
     geef_obj:lookup(Repo, Id, commit).
diff --git a/src/geef_index.erl b/src/geef_index.erl
index 7fbdd90..4ab93eb 100644
--- a/src/geef_index.erl
+++ b/src/geef_index.erl
@@ -27,7 +27,7 @@
 
 %% @doc Create a new index. This index is empty and not associated to
 %% any repository.
--spec new() -> pid().
+-spec new() -> {ok, pid()} | ignore | {error, term()}.
 new() ->
     {ok, Handle} = geef_nif:index_new(),
     start_link(Handle).
@@ -66,6 +66,7 @@ stop(Pid) ->
     gen_server:call(Pid, stop).
 
 %% @private
+-spec start_link(term()) -> {ok, pid()} | ignore | {error, term()}.
 start_link(Handle) ->
     gen_server:start_link(?MODULE, Handle, []).
 
diff --git a/src/geef_nif.erl b/src/geef_nif.erl
index 2d3a436..6ba8fd5 100644
--- a/src/geef_nif.erl
+++ b/src/geef_nif.erl
@@ -75,7 +75,6 @@ odb_write(_Handle, _Contents, _Type) ->
 oid_fmt(_Oid) ->
     nif_error(?LINE).
 
--spec oid_parse(iolist()) -> binary().
 oid_parse(_Sha) ->
     nif_error(?LINE).
 
diff --git a/src/geef_oid.erl b/src/geef_oid.erl
index 8fb6779..4b51350 100644
--- a/src/geef_oid.erl
+++ b/src/geef_oid.erl
@@ -15,7 +15,7 @@ hex(#geef_oid{oid=Oid}) ->
     geef_nif:oid_fmt(Oid).
 
 %% @doc Parse an iolist as a hash
--spec parse(iolist()) -> geef_oid().
+-spec parse(iolist() | binary()) -> geef_oid().
 parse(Sha) ->
     Oid = geef_nif:oid_parse(Sha),
     #geef_oid{oid=Oid}.
diff --git a/src/geef_pkt.erl b/src/geef_pkt.erl
index b17e434..48cdcf8 100644
--- a/src/geef_pkt.erl
+++ b/src/geef_pkt.erl
@@ -56,7 +56,7 @@ do_unpack(Len, Rest) when Len - 4 > size(Rest) ->
 do_unpack(Len, Rest) ->
     {Len - 4, Rest}.
 
--spec parse_pkt(binary(), non_neg_integer()) -> {{want | have}, geef_oid(), binary()} | {done, binary()} | {flush, binary()}.
+-spec parse_pkt(binary(), non_neg_integer()) -> {{want | have, geef_oid()}, binary()} | {done, binary()} | {flush, binary()}.
 parse_pkt(In, 0) ->
     {flush, In};
 parse_pkt(In, Len) ->
@@ -72,6 +72,7 @@ parse_pkt(In, Len) ->
     <<_:LenLF/binary, Rest/binary>> = Rest1,
     {Pkt, Rest}.
 
+-spec pkt_type(binary()) -> {have | want | done, non_neg_integer(), binary()}.
 pkt_type(<<"have ", Rest/binary>>) ->
     {have, 5 + ?SHA_LEN, Rest};
 pkt_type(<<"want ", Rest/binary>>) ->
diff --git a/src/geef_records.hrl b/src/geef_records.hrl
index d59d77d..6b9e4f3 100644
--- a/src/geef_records.hrl
+++ b/src/geef_records.hrl
@@ -1,5 +1,5 @@
--record(geef_reference, {handle, name :: binary(), type :: atom(), target :: binary() | geef_oid()}).
--record(geef_oid, {oid}).
+-record(geef_reference, {handle, name :: binary(), type :: oid | symbolic, target :: binary() | geef_oid()}).
+-record(geef_oid, {oid :: binary()}).
 -record(geef_object, {type :: atom(), id :: geef_oid(), handle}).
 -record(geef_index_entry,
 	{ctime :: non_neg_integer(), mtime :: non_neg_integer(),
@@ -14,8 +14,8 @@
 -record(geef_tree_entry, {mode, type, id, name}).
 -record(geef_signature, {name :: iolist(), email :: iolist(), time :: geef_time()}).
 
--type geef_reference() :: #geef_reference{}.
--type geef_oid() :: #geef_oid{}.
+-type geef_reference() :: #geef_reference{name :: binary(), target :: binary() | geef_oid()}.
+-type geef_oid() :: #geef_oid{oid :: binary()}.
 -type geef_object() :: #geef_object{}.
 -type geef_index_entry() :: #geef_index_entry{}.
 -type geef_request() :: #geef_request{}.
diff --git a/src/geef_ref.erl b/src/geef_ref.erl
index 80fb36e..3716339 100644
--- a/src/geef_ref.erl
+++ b/src/geef_ref.erl
@@ -18,8 +18,12 @@ new(Name, Handle) ->
 
 -spec create(pid(), iolist(), geef_oid() | binary(), boolean()) -> {ok, geef_reference()} | {error, term()}.
 create(Repo, Refname, Target, Force) ->
-    {ok, Ref} = geef_repo:create_reference(Repo, Refname, Target, Force),
-    {ok, new(Refname, Ref)}.
+    case geef_repo:create_reference(Repo, Refname, Target, Force) of
+        {ok, Ref} ->
+            {ok, new(Refname, Ref)};
+        Err = {error, _} ->
+            Err
+    end.
 
 -spec lookup(pid(), iolist()) -> {ok, geef_reference()} | {error, term()}.
 lookup(Repo, Refname) ->
diff --git a/src/geef_tag.erl b/src/geef_tag.erl
index 3112e39..4762c93 100644
--- a/src/geef_tag.erl
+++ b/src/geef_tag.erl
@@ -10,7 +10,7 @@
 
 -spec lookup(pid(), geef_oid() | iolist()) -> {ok, geef_object()} | {error, term()}.
 lookup(Repo, Id) ->
-    geef_object:lookup(Repo, Id, tag).
+    geef_obj:lookup(Repo, Id, tag).
 
 -spec peel(geef_object()) -> {ok, geef_object()} | {error, term()}.
 peel(#geef_object{type=tag, handle=Handle}) ->