diff --git a/prototype/tango-prototype/src/tango_dt.erl b/prototype/tango-prototype/src/tango_dt.erl
index 3eb98fa..a851e27 100644
--- a/prototype/tango-prototype/src/tango_dt.erl
+++ b/prototype/tango-prototype/src/tango_dt.erl
@@ -98,7 +98,7 @@ handle_call({cb_dirty_op, Op}, _From,
 handle_call({cb_pure_op, Op}, _From, #state{cb_mod=CallbackMod} = State) ->
     State2 = #state{i_state=I_State} = roll_log_forward(State),
     Reply = CallbackMod:do_pure_op(Op, I_State),
-    {reply, {ok, Reply}, State2};
+    {reply, Reply, State2};
 handle_call({stop}, _From, State) ->
     {stop, normal, ok, State};
 handle_call(_Request, _From, State) ->
diff --git a/prototype/tango-prototype/src/tango_dt_map.erl b/prototype/tango-prototype/src/tango_dt_map.erl
new file mode 100644
index 0000000..1a4276b
--- /dev/null
+++ b/prototype/tango-prototype/src/tango_dt_map.erl
@@ -0,0 +1,69 @@
+%% -------------------------------------------------------------------
+%%
+%% Copyright (c) 2014 Basho Technologies, Inc.  All Rights Reserved.
+%%
+%% This file is provided to you under the Apache License,
+%% Version 2.0 (the "License"); you may not use this file
+%% except in compliance with the License.  You may obtain
+%% a copy of the License at
+%%
+%%   http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing,
+%% software distributed under the License is distributed on an
+%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+%% KIND, either express or implied.  See the License for the
+%% specific language governing permissions and limitations
+%% under the License.
+%%
+%% -------------------------------------------------------------------
+
+-module(tango_dt_map).
+
+-behaviour(tango_dt).
+
+-export([start_link/4,
+         set/3, get/2]).
+
+%% Tango datatype callbacks
+-export([fresh/0,
+         do_pure_op/2, do_dirty_op/6, play_log_mutate_i_state/3]).
+
+-define(DICTMOD, dict).
+
+-define(LONG_TIME, 30*1000).
+
+start_link(PageSize, SequencerPid, Proj, StreamNum) ->
+    gen_server:start_link(tango_dt,
+                          [PageSize, SequencerPid, Proj, ?MODULE, StreamNum],
+                          []).
+
+set(Pid, Key, Val) ->
+    gen_server:call(Pid, {cb_dirty_op, {o_set, Key, Val}}, ?LONG_TIME).
+
+get(Pid, Key) ->
+    gen_server:call(Pid, {cb_pure_op, {o_get, Key}}, ?LONG_TIME).
+
+
+fresh() ->
+    ?DICTMOD:new().
+
+do_pure_op({o_get, Key}, Dict) ->
+    ?DICTMOD:find(Key, Dict).
+
+do_dirty_op({o_set, _Key, _Val}=Op,
+            I_State, StreamNum, Proj0, PageSize, BackPs) ->
+    Page = term_to_binary(Op),
+    FullPage = tango:pack_v1([{StreamNum, BackPs}], Page, PageSize),
+    {{ok, LPN}, Proj1} = corfurl_client:append_page(Proj0, FullPage,
+                                                    [StreamNum]),
+    NewBackPs = tango:add_back_pointer(BackPs, LPN),
+    {ok, I_State, Proj1, LPN, NewBackPs}.
+
+play_log_mutate_i_state(Pages, _SideEffectsP, I_State) ->
+    lists:foldl(fun({o_set, Key, Val}=_Op, Dict) ->
+                        ?DICTMOD:store(Key, Val, Dict)
+                end,
+                I_State,
+                [binary_to_term(Page) || Page <- Pages]).
+    
diff --git a/prototype/tango-prototype/src/tango_dt_register.erl b/prototype/tango-prototype/src/tango_dt_register.erl
index 9da6f12..3c81e05 100644
--- a/prototype/tango-prototype/src/tango_dt_register.erl
+++ b/prototype/tango-prototype/src/tango_dt_register.erl
@@ -47,7 +47,7 @@ fresh() ->
     undefined.
 
 do_pure_op({o_get}, Register) ->
-    Register.
+    {ok, Register}.
 
 do_dirty_op({o_set, _Val}=Op,
             I_State, StreamNum, Proj0, PageSize, BackPs) ->
diff --git a/prototype/tango-prototype/test/tango_test.erl b/prototype/tango-prototype/test/tango_test.erl
index 2c60d93..b5c1e2e 100644
--- a/prototype/tango-prototype/test/tango_test.erl
+++ b/prototype/tango-prototype/test/tango_test.erl
@@ -193,5 +193,40 @@ tango_dt_register_int(PageSize, Seq, Proj) ->
 
     ok.
 
+tango_dt_map_test() ->
+    ok = run_test("/tmp", "tango_dt_map",
+                  4096, 5*1024, 1, fun tango_dt_map_int/3).
+
+tango_dt_map_int(PageSize, Seq, Proj) ->
+    {ok, OID_Map} = tango_oid:start_link(PageSize, Seq, Proj),
+
+    {ok, Reg1Num} = tango_oid:new(OID_Map, "map1"),
+    {ok, Reg1} = tango_dt_map:start_link(PageSize, Seq, Proj, Reg1Num),
+    {ok, Reg2Num} = tango_oid:new(OID_Map, "map2"),
+    {ok, Reg2} = tango_dt_map:start_link(PageSize, Seq, Proj, Reg2Num),
+
+    NumVals = 8,
+    Vals = [lists:flatten(io_lib:format("version ~w", [X])) ||
+               X <- lists:seq(1, NumVals)],
+    Keys = ["key1", "key2"],
+    [tango_dt_map:set(Reg, Key, Val) || Reg <- [Reg1, Reg2],
+                                        Key <- Keys, Val <- Vals],
+    LastVal = lists:last(Vals),
+    [{ok, LastVal} = tango_dt_map:get(Reg1, Key) || Key <- Keys],
+    [{ok, LastVal} = tango_dt_map:get(Reg2, Key) || Key <- Keys],
+
+    %% If we instantiate a new instance of an existing map, then
+    %% a single get should show the most recent modification.
+    {ok, Reg2b} = tango_dt_map:start_link(PageSize, Seq, Proj, Reg2Num),
+    [{ok, LastVal} = tango_dt_map:get(Reg2b, Key) || Key <- Keys],
+    %% If we update the "old" instance of a map, then the "new"
+    %% instance should also see the update.
+    NewVal = {"Heh", "a new value"},
+    [ok = tango_dt_map:set(Reg2, Key, NewVal) || Key <- Keys],
+    [{ok, NewVal} = tango_dt_map:get(Reg2b, Key) || Key <- Keys],
+    [{ok, NewVal} = tango_dt_map:get(Reg2, Key) || Key <- Keys], % sanity
+
+    ok.
+
 -endif. % not PULSE
 -endif. % TEST