diff --git a/c/pthread/sync/_pthd/pthd.c b/c/pthread/sync/_pthd/pthd.c
index e8275a54..f7bc7eb9 100644
--- a/c/pthread/sync/_pthd/pthd.c
+++ b/c/pthread/sync/_pthd/pthd.c
@@ -5,3 +5,15 @@
 pthread_once_t llgoSyncOnceInitVal = PTHREAD_ONCE_INIT;
 
 // -----------------------------------------------------------------------------
+
+// wrap return type to void
+void wrap_pthread_mutex_lock(pthread_mutex_t *mutex) {
+    pthread_mutex_lock(mutex);
+}
+
+// wrap return type to void
+void wrap_pthread_mutex_unlock(pthread_mutex_t *mutex) {
+    pthread_mutex_unlock(mutex);
+}
+
+// -----------------------------------------------------------------------------
diff --git a/c/pthread/sync/sync.go b/c/pthread/sync/sync.go
index 8c9ce5db..b9e45d48 100644
--- a/c/pthread/sync/sync.go
+++ b/c/pthread/sync/sync.go
@@ -76,18 +76,14 @@ func (m *Mutex) Init(attr *MutexAttr) c.Int { return 0 }
 // llgo:link (*Mutex).Destroy C.pthread_mutex_destroy
 func (m *Mutex) Destroy() {}
 
-func (m *Mutex) Lock() { m.lockInternal() }
-
-// llgo:link (*Mutex).lockInternal C.pthread_mutex_lock
-func (m *Mutex) lockInternal() c.Int { return 0 }
-
 // llgo:link (*Mutex).TryLock C.pthread_mutex_trylock
 func (m *Mutex) TryLock() c.Int { return 0 }
 
-func (m *Mutex) Unlock() { m.unlockInternal() }
+// llgo:link (*Mutex).Lock C.wrap_pthread_mutex_lock
+func (m *Mutex) Lock() {}
 
-// llgo:link (*Mutex).unlockInternal C.pthread_mutex_unlock
-func (m *Mutex) unlockInternal() c.Int { return 0 }
+// llgo:link (*Mutex).Unlock C.wrap_pthread_mutex_unlock
+func (m *Mutex) Unlock() {}
 
 // -----------------------------------------------------------------------------