diff --git a/ostd/channel.hh b/ostd/channel.hh
index bd90182..bee7323 100644
--- a/ostd/channel.hh
+++ b/ostd/channel.hh
@@ -70,15 +70,17 @@ private:
         impl() {}
 
         template<typename F>
-        impl(F &func): p_lock(), p_cond(func(p_lock)) {}
+        impl(F &func): p_lock(), p_cond(func()) {}
 
         template<typename U>
         void put(U &&val) {
-            std::lock_guard<std::mutex> l{p_lock};
-            if (p_closed) {
-                throw channel_error{"put in a closed channel"};
+            {
+                std::lock_guard<std::mutex> l{p_lock};
+                if (p_closed) {
+                    throw channel_error{"put in a closed channel"};
+                }
+                p_messages.push_back(std::forward<U>(val));
             }
-            p_messages.push_back(std::forward<U>(val));
             p_cond.notify_one();
         }
 
@@ -106,8 +108,10 @@ private:
         }
 
         void close() {
-            std::lock_guard<std::mutex> l{p_lock};
-            p_closed = true;
+            {
+                std::lock_guard<std::mutex> l{p_lock};
+                p_closed = true;
+            }
             p_cond.notify_all();
         }
 
diff --git a/ostd/concurrency.hh b/ostd/concurrency.hh
index e95c532..8d14592 100644
--- a/ostd/concurrency.hh
+++ b/ostd/concurrency.hh
@@ -88,9 +88,7 @@ private:
         coro_cond &operator=(coro_cond const &) = delete;
         coro_cond &operator=(coro_cond &&) = delete;
 
-        coro_cond(basic_simple_coroutine_scheduler &s, std::mutex &mtx):
-            p_sched(s), p_mtx(mtx)
-        {}
+        coro_cond(basic_simple_coroutine_scheduler &s): p_sched(s) {}
 
         template<typename L>
         void wait(L &l) noexcept {
@@ -104,20 +102,15 @@ private:
 
         void notify_one() noexcept {
             p_notified = true;
-            p_mtx.unlock();
             p_sched.yield();
-            p_mtx.lock();
         }
 
         void notify_all() noexcept {
             p_notified = true;
-            p_mtx.unlock();
             p_sched.yield();
-            p_mtx.lock();
         }
     private:
         basic_simple_coroutine_scheduler &p_sched;
-        std::mutex &p_mtx;
         bool p_notified = false;
     };
 
@@ -182,8 +175,8 @@ public:
 
     template<typename T>
     channel<T, coro_cond> make_channel() {
-        return channel<T, coro_cond>{[this](std::mutex &mtx) {
-            return coro_cond{*this, mtx};
+        return channel<T, coro_cond>{[this]() {
+            return coro_cond{*this};
         }};
     }
 private: