diff --git a/libs/async/include/psemek/async/future.hpp b/libs/async/include/psemek/async/future.hpp
index e6863889..0945aed5 100644
--- a/libs/async/include/psemek/async/future.hpp
+++ b/libs/async/include/psemek/async/future.hpp
@@ -55,7 +55,8 @@ namespace psemek::async
 			std::weak_ptr<cancel_token> weak_cancel;
 
 			std::mutex then_mutex;
-			typename then_function<T>::type then_func;
+			std::vector<typename then_function<T>::type> then_funcs;
+			std::vector<util::function<void(std::exception_ptr)>> then_exception_funcs;
 		};
 
 	}
@@ -85,14 +86,16 @@ namespace psemek::async
 		using result_type = T;
 
 		future() = default;
-		future(future&&) = default;
+		future(future const &) = default;
+		future(future &&) = default;
 
 		future(std::shared_ptr<detail::task_state<T>> state, std::shared_ptr<detail::cancel_token> cancel)
 			: state_(std::move(state))
 			, cancel_(std::move(cancel))
 		{}
 
-		future & operator = (future&&) = default;
+		future & operator = (future const &) = default;
+		future & operator = (future &&) = default;
 
 		~future()
 		{
@@ -239,8 +242,10 @@ namespace psemek::async
 				state_->value = value;
 			}
 			state_->value_cv.notify_all();
-			if (state_->then_func)
-				state_->then_func(*state_->value);
+
+			std::lock_guard lock{state_->then_mutex};
+			for (auto & func : state_->then_funcs)
+				func(*state_->value);
 		}
 
 		void set_value(T && value)
@@ -252,8 +257,10 @@ namespace psemek::async
 				state_->value = std::move(value);
 			}
 			state_->value_cv.notify_all();
-			if (state_->then_func)
-				state_->then_func(*state_->value);
+
+			std::lock_guard lock{state_->then_mutex};
+			for (auto & func : state_->then_funcs)
+				func(*state_->value);
 		}
 
 		void set_exception(std::exception_ptr e)
@@ -263,6 +270,10 @@ namespace psemek::async
 				std::lock_guard lock{state_->value_mutex};
 				if (state_->value || state_->exception) throw satisfied_promise_error{};
 				state_->exception = std::move(e);
+
+				std::lock_guard lock_then{state_->then_mutex};
+				for (auto & func : state_->then_exception_funcs)
+					func(state_->exception);
 			}
 			state_->value_cv.notify_all();
 		}
@@ -324,8 +335,10 @@ namespace psemek::async
 				state_->value = true;
 			}
 			state_->value_cv.notify_all();
-			if (state_->then_func)
-				state_->then_func();
+
+			std::lock_guard lock{state_->then_mutex};
+			for (auto & func : state_->then_funcs)
+				func();
 		}
 
 		void set_exception(std::exception_ptr e)
@@ -335,6 +348,10 @@ namespace psemek::async
 				std::lock_guard lock{state_->value_mutex};
 				if (state_->value || state_->exception) throw satisfied_promise_error{};
 				state_->exception = std::move(e);
+
+				std::lock_guard lock_then{state_->then_mutex};
+				for (auto & func : state_->then_exception_funcs)
+					func(state_->exception);
 			}
 			state_->value_cv.notify_all();
 		}
@@ -488,7 +505,7 @@ namespace psemek::async
 			auto fut = t.get_future();
 
 			std::lock_guard lock{state_->then_mutex};
-			state_->then_func = std::move(t);
+			state_->then_funcs.push_back(std::move(t));
 			return fut;
 		}
 		else
@@ -498,7 +515,7 @@ namespace psemek::async
 			auto fut = t.get_future();
 
 			std::lock_guard lock{state_->then_mutex};
-			state_->then_func = std::move(t);
+			state_->then_funcs.push_back(std::move(t));
 			return fut;
 		}
 	}