diff --git a/c_src/quicer_nif.c b/c_src/quicer_nif.c
index 1a9a1239..66e2fc24 100644
--- a/c_src/quicer_nif.c
+++ b/c_src/quicer_nif.c
@@ -1364,9 +1364,11 @@ controlling_process(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
   ErlNifPid target, caller;
   ERL_NIF_TERM new_owner = argv[1];
   ERL_NIF_TERM res = ATOM_OK;
-  if (argc != 2)
+  BOOLEAN is_locked = FALSE;
+  if (argc == 3 || IS_SAME_TERM(argv[2], ATOM_TRUE))
     {
-      return ATOM_BADARG;
+      // give hint to this call that stream mutex is locked.
+      is_locked = TRUE;
     }
 
   // precheck
@@ -1388,7 +1390,10 @@ controlling_process(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
           return ERROR_TUPLE_2(ATOM_CLOSED);
         }
 
-      enif_mutex_lock(s_ctx->lock);
+      if (!is_locked)
+        {
+          enif_mutex_lock(s_ctx->lock);
+        }
       res = stream_controlling_process(env, s_ctx, &caller, &new_owner);
       enif_mutex_unlock(s_ctx->lock);
       put_stream_handle(s_ctx);
@@ -1561,6 +1566,7 @@ static ErlNifFunc nif_funcs[] = {
   { "getopt", 3, getopt3, 0},
   { "setopt", 4, setopt4, 0},
   { "controlling_process", 2, controlling_process, 0},
+  { "controlling_process", 3, controlling_process, 0},
   { "peercert", 1, peercert1, 0},
   /* for DEBUG */
   { "get_conn_rid", 1, get_conn_rid1, 1},
@@ -1571,7 +1577,9 @@ static ErlNifFunc nif_funcs[] = {
   { "get_connections", 1, get_connectionsX, 0},
   { "get_conn_owner", 1, get_conn_owner1, 0},
   { "get_stream_owner", 1, get_stream_owner1, 0},
-  { "get_listener_owner", 1, get_listener_owner1, 0}
+  { "get_listener_owner", 1, get_listener_owner1, 0},
+  { "lock_stream", 1, lock_stream, 0},
+  { "unlock_stream", 1, unlock_stream, 0}
   // clang-format on
 };
 
diff --git a/c_src/quicer_stream.c b/c_src/quicer_stream.c
index 0acbadcf..f6ad317d 100644
--- a/c_src/quicer_stream.c
+++ b/c_src/quicer_stream.c
@@ -1268,6 +1268,35 @@ get_stream_owner1(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
   return res;
 }
 
+ERL_NIF_TERM
+lock_stream(ErlNifEnv *env,
+            __unused_parm__ int args,
+            const ERL_NIF_TERM argv[])
+{
+  QuicerStreamCTX *s_ctx;
+  if (!enif_get_resource(env, argv[0], ctx_stream_t, (void **)&s_ctx))
+    {
+      return ERROR_TUPLE_2(ATOM_BADARG);
+    }
+  enif_mutex_lock(s_ctx->lock);
+  return ATOM_OK;
+}
+
+ERL_NIF_TERM
+unlock_stream(ErlNifEnv *env,
+              __unused_parm__ int args,
+              const ERL_NIF_TERM argv[])
+{
+  QuicerStreamCTX *s_ctx;
+  if (!enif_get_resource(env, argv[0], ctx_stream_t, (void **)&s_ctx))
+    {
+      return ERROR_TUPLE_2(ATOM_BADARG);
+    }
+
+  enif_mutex_unlock(s_ctx->lock);
+  return ATOM_OK;
+}
+
 ///_* Emacs
 ///====================================================================
 /// Local Variables:
diff --git a/c_src/quicer_stream.h b/c_src/quicer_stream.h
index 4037d68a..9b7f5c89 100644
--- a/c_src/quicer_stream.h
+++ b/c_src/quicer_stream.h
@@ -66,3 +66,9 @@ get_stream_rid1(ErlNifEnv *env, int args, const ERL_NIF_TERM argv[]);
 
 ERL_NIF_TERM
 get_stream_owner1(ErlNifEnv *env, int args, const ERL_NIF_TERM argv[]);
+
+ERL_NIF_TERM
+lock_stream(ErlNifEnv *env, int args, const ERL_NIF_TERM argv[]);
+
+ERL_NIF_TERM
+unlock_stream(ErlNifEnv *env, int args, const ERL_NIF_TERM argv[]);
diff --git a/src/quicer.erl b/src/quicer.erl
index e161450e..18d0d2ff 100644
--- a/src/quicer.erl
+++ b/src/quicer.erl
@@ -1150,13 +1150,20 @@ handoff_stream(Stream, NewOwner, HandoffData) ->
     case quicer:getopt(Stream, active) of
         {ok, ActiveN} ->
             ActiveN =/= false andalso quicer:setopt(Stream, active, false),
+            ok = quicer_nif:lock_stream(Stream),
             Res =
                 case forward_stream_msgs(Stream, NewOwner) of
                     ok ->
-                        _ = quicer:controlling_process(Stream, NewOwner),
+                        case quicer_nif:controlling_process(Stream, NewOwner, true) of
+                            {error, _} ->
+                                quicer_nif:unlock_stream(Stream);
+                            ok ->
+                                ok
+                        end,
                         NewOwner ! {handoff_done, Stream, HandoffData},
                         ok;
                     {error, _} = Other ->
+                        quicer_nif:unlock_stream(Stream),
                         Other
                 end,
             ActiveN =/= false andalso quicer:setopt(Stream, active, ActiveN),
diff --git a/src/quicer_nif.erl b/src/quicer_nif.erl
index 2b03d3f7..354a53ae 100644
--- a/src/quicer_nif.erl
+++ b/src/quicer_nif.erl
@@ -44,7 +44,10 @@
     getopt/3,
     setopt/4,
     controlling_process/2,
-    peercert/1
+    controlling_process/3,
+    peercert/1,
+    lock_stream/1,
+    unlock_stream/1
 ]).
 
 -export([
@@ -337,11 +340,25 @@ get_stream_rid(_Handle) ->
 controlling_process(_H, _P) ->
     erlang:nif_error(nif_library_not_loaded).
 
+-spec controlling_process(connection_handle() | stream_handle(), pid(), boolean()) ->
+    ok
+    | {error, closed | badarg | owner_dead | not_owner}.
+controlling_process(_H, _P, IsLocked) ->
+    erlang:nif_error(nif_library_not_loaded).
+
 -spec peercert(connection_handle() | stream_handle()) ->
     {ok, CertDerEncoded :: binary()} | {error, any()}.
 peercert(_Handle) ->
     erlang:nif_error(nif_library_not_loaded).
 
+-spec lock_stream(stream_handle()) -> ok | {error, badarg}.
+lock_stream(_Handle) ->
+    erlang:nif_error(nif_library_not_loaded).
+
+-spec unlock_stream(stream_handle()) -> ok | {error, badarg}.
+unlock_stream(_Handle) ->
+    erlang:nif_error(nif_library_not_loaded).
+
 -spec get_conn_owner(connection_handle()) -> get_owner().
 get_conn_owner(_) ->
     erlang:nif_error(nif_library_not_loaded).