diff --git a/include/fc/thread/future.hpp b/include/fc/thread/future.hpp
index 7233274..4068dd0 100644
--- a/include/fc/thread/future.hpp
+++ b/include/fc/thread/future.hpp
@@ -13,7 +13,7 @@
 # define FC_TASK_NAME_DEFAULT_ARG = "?"
 #endif
 
-#define FC_CANCELATION_REASONS_ARE_MANDATORY 1
+//#define FC_CANCELATION_REASONS_ARE_MANDATORY 1
 #ifdef FC_CANCELATION_REASONS_ARE_MANDATORY
 # define FC_CANCELATION_REASON_DEFAULT_ARG
 #else
@@ -98,7 +98,11 @@ namespace fc {
       time_point                  _timeout;
       fc::exception_ptr           _exceptp;
       bool                        _canceled;
+#ifndef NDEBUG
+    protected:
       const char*                 _cancellation_reason;
+    private:
+#endif
       const char*                 _desc;
       detail::completion_handler* _compl;
   };
diff --git a/src/thread/context.hpp b/src/thread/context.hpp
index ecd360f..fdede1d 100644
--- a/src/thread/context.hpp
+++ b/src/thread/context.hpp
@@ -111,6 +111,21 @@ namespace fc {
 #endif
     }
 
+    void reinitialize()
+    {
+      canceled = false;
+#ifndef NDEBUG
+      cancellation_reason = nullptr;
+#endif
+      blocking_prom.clear();
+      caller_context = nullptr;
+      resume_time = fc::time_point();
+      next_blocked = nullptr;
+      next_blocked_mutex = nullptr;
+      next = nullptr;
+      complete = false;
+    }
+
     struct blocked_promise {
       blocked_promise( promise_base* p=0, bool r=true )
       :prom(p),required(r){}
@@ -168,7 +183,7 @@ namespace fc {
         i->prom->set_exception( std::make_shared<timeout_exception>() );
       }
     }
-    void except_blocking_promises( const exception_ptr& e ) {
+    void set_exception_on_blocking_promises( const exception_ptr& e ) {
       for( auto i = blocking_prom.begin(); i != blocking_prom.end(); ++i ) {
         i->prom->set_exception( e );
       }
diff --git a/src/thread/future.cpp b/src/thread/future.cpp
index 9ad6648..92d4fea 100644
--- a/src/thread/future.cpp
+++ b/src/thread/future.cpp
@@ -30,11 +30,11 @@ namespace fc {
                
   void promise_base::cancel(const char* reason /* = nullptr */){
 //      wlog("${desc} canceled!", ("desc", _desc? _desc : ""));
-    _canceled = true;
+      _canceled = true;
 #ifndef NDEBUG
-    _cancellation_reason = reason;
+      _cancellation_reason = reason;
 #endif
-  }
+    }
   bool promise_base::ready()const {
     return _ready;
   }
diff --git a/src/thread/task.cpp b/src/thread/task.cpp
index 46af23f..4d9acfc 100644
--- a/src/thread/task.cpp
+++ b/src/thread/task.cpp
@@ -42,7 +42,13 @@ namespace fc {
       if( !canceled() )
          _run_functor( _functor, _promise_impl  );
       else
-         FC_THROW_EXCEPTION( canceled_exception, "${description}", ("description", get_desc() ) );
+#ifdef NDEBUG
+         FC_THROW_EXCEPTION( canceled_exception, "task ${description} canceled before starting", ("description", get_desc()));
+#else
+         FC_THROW_EXCEPTION( canceled_exception, "task ${description} canceled before starting, reason ${reason}", 
+                             ("description", get_desc())
+                             ("reason", _cancellation_reason ? _cancellation_reason : "[none given]"));
+#endif
     } 
     catch ( const exception& e ) 
     {
diff --git a/src/thread/thread.cpp b/src/thread/thread.cpp
index ae9486b..e9b8efb 100644
--- a/src/thread/thread.cpp
+++ b/src/thread/thread.cpp
@@ -157,8 +157,8 @@ namespace fc {
             fc::context* n = cur->next;
             // this will move the context into the ready list.
             //cur->prom->set_exception( boost::copy_exception( error::thread_quit() ) );
-            //cur->except_blocking_promises( thread_quit() );
-            cur->except_blocking_promises( std::make_shared<canceled_exception>() );
+            //cur->set_exception_on_blocking_promises( thread_quit() );
+            cur->set_exception_on_blocking_promises( std::make_shared<canceled_exception>(FC_LOG_MESSAGE(error, "cancellation reason: thread quitting")) );
                
             cur = n;
         }
diff --git a/src/thread/thread_d.hpp b/src/thread/thread_d.hpp
index 48a8879..af6e6b0 100644
--- a/src/thread/thread_d.hpp
+++ b/src/thread/thread_d.hpp
@@ -284,10 +284,14 @@ namespace fc {
             */
            void check_fiber_exceptions() {
               if( current && current->canceled ) {
+#ifdef NDEBUG
                 FC_THROW_EXCEPTION( canceled_exception, "" );
+#else
+                FC_THROW_EXCEPTION( canceled_exception, "cancellation reason: ${reason}", ("reason", current->cancellation_reason ? current->cancellation_reason : "[none given]"));
+#endif
               } else if( done )  {
                 ilog( "throwing canceled exception" );
-                FC_THROW_EXCEPTION( canceled_exception, "" ); 
+                FC_THROW_EXCEPTION( canceled_exception, "cancellation reason: thread quitting" ); 
              //   BOOST_THROW_EXCEPTION( thread_quit() );
               }
            }
@@ -335,6 +339,7 @@ namespace fc {
                   next = pt_head;
                   pt_head = pt_head->next;
                   next->next = 0;
+                  next->reinitialize();
                 } else { // create new context.
                   next = new fc::context( &thread_d::start_process_tasks, stack_alloc,
                                                                       &fc::thread::current() );
@@ -356,8 +361,12 @@ namespace fc {
               }
 
               if( current->canceled ) {
-                   current->canceled = false;
-                   FC_THROW_EXCEPTION( canceled_exception, "" );
+                //current->canceled = false;
+#ifdef NDEBUG
+                FC_THROW_EXCEPTION( canceled_exception, "" );
+#else
+                FC_THROW_EXCEPTION( canceled_exception, "cancellation reason: ${reason}", ("reason", current->cancellation_reason ? current->cancellation_reason : "[none given]"));
+#endif
               }
 
               return true;
@@ -390,6 +399,7 @@ namespace fc {
                     current->cur_task = 0;
                     next->_set_active_context(0);
                     next->release();
+                    current->reinitialize();
                     return true;
                 }
                 return false;