diff --git a/src/libp2p_multistream_client.erl b/src/libp2p_multistream_client.erl
index 9c306889..de25a67a 100644
--- a/src/libp2p_multistream_client.erl
+++ b/src/libp2p_multistream_client.erl
@@ -23,7 +23,9 @@ negotiate_handler(Handlers0, Path, Connection) ->
                 {error, Error} ->
                     lager:notice("Failed to negotiate handler for ~p: ~p", [Path, Error]),
                     {error, Error};
-                {_, Handler} -> {ok, Handler}
+                {_, Handler = {_Path, {M, _F}}} ->
+                    put('__multistream_client_handler', M),
+                    {ok, Handler}
             end
     end.
 
diff --git a/src/libp2p_multistream_server.erl b/src/libp2p_multistream_server.erl
index d5ef4cb2..5622325a 100644
--- a/src/libp2p_multistream_server.erl
+++ b/src/libp2p_multistream_server.erl
@@ -57,6 +57,7 @@ handle_msg(Msg, State) ->
         {noreply, NewState} ->
             loop(NewState);
         {exec, M, F, A} ->
+            put('__multistream_server_handler', M),
             erlang:cancel_timer(State#state.timeout),
             try erlang:apply(M, F, A) of
                 Result -> Result