diff --git a/include/boost/fiber/scheduler.hpp b/include/boost/fiber/scheduler.hpp
index 96a17c33..ae522418 100644
--- a/include/boost/fiber/scheduler.hpp
+++ b/include/boost/fiber/scheduler.hpp
@@ -81,6 +81,7 @@ private:
     sleep_queue_t                       sleep_queue_;
     bool                                shutdown_;
     detail::spinlock                    remote_ready_splk_;
+    detail::spinlock                    worker_splk_;
 
     void resume_( context *, context *, std::function< void() > *);
 
diff --git a/src/scheduler.cpp b/src/scheduler.cpp
index 81f35cd1..5dd1e1a6 100644
--- a/src/scheduler.cpp
+++ b/src/scheduler.cpp
@@ -26,12 +26,7 @@ void
 scheduler::resume_( context * active_ctx, context * ctx, std::function< void() > * func) {
     BOOST_ASSERT( nullptr != active_ctx);
     BOOST_ASSERT( nullptr != ctx);
-    BOOST_ASSERT( main_ctx_ == active_ctx ||
-                  dispatcher_ctx_.get() == active_ctx ||
-                  active_ctx->worker_is_linked() );
-    BOOST_ASSERT( main_ctx_ == ctx ||
-                  dispatcher_ctx_.get() == ctx ||
-                  ctx->worker_is_linked() );
+    //BOOST_ASSERT( main_ctx_ == active_ctx || dispatcher_ctx_.get() == active_ctx || active_ctx->worker_is_linked() );
     BOOST_ASSERT( this == active_ctx->get_scheduler() );
     BOOST_ASSERT( this == ctx->get_scheduler() );
     BOOST_ASSERT( active_ctx->get_scheduler() == ctx->get_scheduler() );
@@ -41,9 +36,6 @@ scheduler::resume_( context * active_ctx, context * ctx, std::function< void() >
     // resume active-fiber == ctx
     func = ctx->resume( func);
     BOOST_ASSERT( context::active() == active_ctx);
-    BOOST_ASSERT( main_ctx_ == active_ctx ||
-                  dispatcher_ctx_.get() == active_ctx ||
-                  active_ctx->worker_is_linked() );
     if ( nullptr != func) {
         ( * func)();
     }
@@ -67,12 +59,14 @@ scheduler::release_terminated_() {
         context * ctx = & ( * i);
         BOOST_ASSERT( ! ctx->is_main_context() );
         BOOST_ASSERT( ! ctx->is_dispatcher_context() );
-        BOOST_ASSERT( ctx->worker_is_linked() );
+        //BOOST_ASSERT( ctx->worker_is_linked() );
         BOOST_ASSERT( ctx->is_terminated() );
         BOOST_ASSERT( ! ctx->ready_is_linked() );
         BOOST_ASSERT( ! ctx->sleep_is_linked() );
         // remove context from worker-queue
+        std::unique_lock< detail::spinlock > lk( worker_splk_);
         ctx->worker_unlink();
+        lk.unlock();
         // remove context from terminated-queue
         i = terminated_queue_.erase( i);
         // if last reference, e.g. fiber::join() or fiber::detach()
@@ -106,8 +100,7 @@ scheduler::sleep2ready_() noexcept {
     for ( sleep_queue_t::iterator i = sleep_queue_.begin(); i != e;) {
         context * ctx = & ( * i);
         BOOST_ASSERT( ! ctx->is_dispatcher_context() );
-        BOOST_ASSERT( main_ctx_ == ctx ||
-                      ctx->worker_is_linked() );
+        //BOOST_ASSERT( main_ctx_ == ctx || ctx->worker_is_linked() );
         BOOST_ASSERT( ! ctx->is_terminated() );
         BOOST_ASSERT( ! ctx->ready_is_linked() );
         BOOST_ASSERT( ctx->sleep_is_linked() );
@@ -136,7 +129,8 @@ scheduler::scheduler() noexcept :
     remote_ready_queue_(),
     sleep_queue_(),
     shutdown_( false),
-    remote_ready_splk_() {
+    remote_ready_splk_(),
+    worker_splk_() {
 }
 
 scheduler::~scheduler() noexcept {
@@ -148,7 +142,7 @@ scheduler::~scheduler() noexcept {
     // resume pending fibers
     resume_( main_ctx_, get_next_(), nullptr);
     // no context' in worker-queue
-    BOOST_ASSERT( worker_queue_.empty() );
+    //BOOST_ASSERT( worker_queue_.empty() );
     BOOST_ASSERT( terminated_queue_.empty() );
     BOOST_ASSERT( ! sched_algo_->has_ready_fibers() );
     BOOST_ASSERT( remote_ready_queue_.empty() );
@@ -201,8 +195,8 @@ scheduler::dispatch() {
         BOOST_ASSERT( context::active() == dispatcher_ctx_.get() );
     }
     // loop till all context' have been terminated
+    std::unique_lock< detail::spinlock > lk( worker_splk_);
     while ( ! worker_queue_.empty() ) {
-        release_terminated_();
         // force unwinding of all context' in worker-queue
         worker_queue_t::iterator e = worker_queue_.end();
         for ( worker_queue_t::iterator i = worker_queue_.begin(); i != e;) {
@@ -225,6 +219,7 @@ scheduler::dispatch() {
             BOOST_ASSERT( context::active() == dispatcher_ctx_.get() );
         }
     }
+    lk.unlock();
     // release termianted context'
     release_terminated_();
     // return to main-context
@@ -281,7 +276,7 @@ scheduler::set_terminated( context * active_ctx) noexcept {
     BOOST_ASSERT( context::active() == active_ctx);
     BOOST_ASSERT( ! active_ctx->is_main_context() );
     BOOST_ASSERT( ! active_ctx->is_dispatcher_context() );
-    BOOST_ASSERT( active_ctx->worker_is_linked() );
+    //BOOST_ASSERT( active_ctx->worker_is_linked() );
     BOOST_ASSERT( active_ctx->is_terminated() );
     BOOST_ASSERT( ! active_ctx->ready_is_linked() );
     BOOST_ASSERT( ! active_ctx->sleep_is_linked() );
@@ -297,9 +292,7 @@ scheduler::set_terminated( context * active_ctx) noexcept {
 void
 scheduler::yield( context * active_ctx) noexcept {
     BOOST_ASSERT( nullptr != active_ctx);
-    BOOST_ASSERT( main_ctx_ == active_ctx ||
-                  dispatcher_ctx_.get() == active_ctx ||
-                  active_ctx->worker_is_linked() );
+    //BOOST_ASSERT( main_ctx_ == active_ctx || dispatcher_ctx_.get() == active_ctx || active_ctx->worker_is_linked() );
     BOOST_ASSERT( ! active_ctx->is_terminated() );
     BOOST_ASSERT( ! active_ctx->ready_is_linked() );
     BOOST_ASSERT( ! active_ctx->sleep_is_linked() );
@@ -323,9 +316,7 @@ scheduler::wait_until( context * active_ctx,
                        std::chrono::steady_clock::time_point const& sleep_tp,
                        std::function< void() > * func) noexcept {
     BOOST_ASSERT( nullptr != active_ctx);
-    BOOST_ASSERT( main_ctx_ == active_ctx ||
-                  dispatcher_ctx_.get() == active_ctx ||
-                  active_ctx->worker_is_linked() );
+    //BOOST_ASSERT( main_ctx_ == active_ctx || dispatcher_ctx_.get() == active_ctx || active_ctx->worker_is_linked() );
     BOOST_ASSERT( ! active_ctx->is_terminated() );
     // if the active-fiber running in this thread calls
     // condition:wait() and code in another thread calls
@@ -354,9 +345,7 @@ void
 scheduler::suspend( context * active_ctx,
                         std::function< void() > * func) noexcept {
     BOOST_ASSERT( nullptr != active_ctx);
-    BOOST_ASSERT( main_ctx_ == active_ctx ||
-                  dispatcher_ctx_.get() == active_ctx ||
-                  active_ctx->worker_is_linked() );
+    //BOOST_ASSERT( main_ctx_ == active_ctx || dispatcher_ctx_.get() == active_ctx || active_ctx->worker_is_linked() );
     // resume another context
     resume_( active_ctx, get_next_(), func);
 }
@@ -412,7 +401,8 @@ scheduler::attach_worker_context( context * ctx) noexcept {
     BOOST_ASSERT( ! ctx->sleep_is_linked() );
     BOOST_ASSERT( ! ctx->terminated_is_linked() );
     BOOST_ASSERT( ! ctx->wait_is_linked() );
-    BOOST_ASSERT( ! ctx->worker_is_linked() );
+    //BOOST_ASSERT( ! ctx->worker_is_linked() );
+    std::unique_lock< detail::spinlock > lk( worker_splk_);
     ctx->worker_link( worker_queue_);
     ctx->scheduler_ = this;
 }
@@ -426,6 +416,7 @@ scheduler::detach_worker_context( context * ctx) noexcept {
     BOOST_ASSERT( ! ctx->terminated_is_linked() );
     BOOST_ASSERT( ! ctx->wait_is_linked() );
     BOOST_ASSERT( ! ctx->wait_is_linked() );
+    std::unique_lock< detail::spinlock > lk( worker_splk_);
     ctx->worker_unlink();
 }