diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 41cb23d..50a29d8 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -307,11 +307,13 @@
 #else
 static inline void futex_wake(QemuEvent *ev, int n)
 {
+    pthread_mutex_lock(&ev->lock);
     if (n == 1) {
         pthread_cond_signal(&ev->cond);
     } else {
         pthread_cond_broadcast(&ev->cond);
     }
+    pthread_mutex_unlock(&ev->lock);
 }
 
 static inline void futex_wait(QemuEvent *ev, unsigned val)