diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index 8d55663062..dfd261c5b1 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -167,6 +167,21 @@ void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
  */
 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
 
+/**
+ * Assert that the current coroutine holds @mutex.
+ */
+static inline coroutine_fn void qemu_co_mutex_assert_locked(CoMutex *mutex)
+{
+    /*
+     * mutex->holder doesn't need any synchronisation if the assertion holds
+     * true because the mutex protects it. If it doesn't hold true, we still
+     * don't mind if another thread takes or releases mutex behind our back,
+     * because the condition will be false no matter whether we read NULL or
+     * the pointer for any other coroutine.
+     */
+    assert(atomic_read(&mutex->locked) &&
+           mutex->holder == qemu_coroutine_self());
+}
 
 /**
  * CoQueues are a mechanism to queue coroutines in order to continue executing