diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index ac8d4c9cc8..29a20782f0 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -143,6 +143,7 @@ bool qemu_co_queue_empty(CoQueue *queue);
  */
 typedef struct CoMutex {
     bool locked;
+    Coroutine *holder;
     CoQueue queue;
 } CoMutex;
 
diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index 22aa9abb30..f30ee8184d 100644
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -129,6 +129,7 @@ void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
     }
 
     mutex->locked = true;
+    mutex->holder = self;
 
     trace_qemu_co_mutex_lock_return(mutex, self);
 }
@@ -140,9 +141,11 @@ void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
     trace_qemu_co_mutex_unlock_entry(mutex, self);
 
     assert(mutex->locked == true);
+    assert(mutex->holder == self);
     assert(qemu_in_coroutine());
 
     mutex->locked = false;
+    mutex->holder = NULL;
     qemu_co_queue_next(&mutex->queue);
 
     trace_qemu_co_mutex_unlock_return(mutex, self);