diff --git a/libc/include/sys/sem.h b/libc/include/sys/sem.h
index be0e22d..cd62242 100644
--- a/libc/include/sys/sem.h
+++ b/libc/include/sys/sem.h
@@ -51,12 +51,12 @@
   void* __pad;
 };
 
-int semctl(int, int, int, ...) __INTRODUCED_IN(26);
-int semget(key_t, int, int) __INTRODUCED_IN(26);
-int semop(int, struct sembuf*, size_t) __INTRODUCED_IN(26);
+int semctl(int __sem_id, int __sem_num, int __cmd, ...) __INTRODUCED_IN(26);
+int semget(key_t __key, int __sem_count, int __flags) __INTRODUCED_IN(26);
+int semop(int __sem_id, struct sembuf* __ops, size_t __op_count) __INTRODUCED_IN(26);
 
 #if defined(__USE_GNU)
-int semtimedop(int, struct sembuf*, size_t, const struct timespec*) __INTRODUCED_IN(26);
+int semtimedop(int __sem_id, struct sembuf* __ops, size_t __op_count, const struct timespec* __timeout) __INTRODUCED_IN(26);
 #endif
 
 __END_DECLS