diff --git a/libc/include/semaphore.h b/libc/include/semaphore.h
index 30e3123..7ae3c3a 100644
--- a/libc/include/semaphore.h
+++ b/libc/include/semaphore.h
@@ -33,10 +33,13 @@
 __BEGIN_DECLS
 
 typedef struct {
-    volatile unsigned int  count;
+  volatile unsigned int count;
+#ifdef __LP64__
+  int __reserved[3];
+#endif
 } sem_t;
 
-#define  SEM_FAILED  NULL
+#define SEM_FAILED NULL
 
 extern int sem_init(sem_t *sem, int pshared, unsigned int value);