diff --git a/tests/sys_shm_test.cpp b/tests/sys_shm_test.cpp
index cf7f3a5..ca2d01a 100644
--- a/tests/sys_shm_test.cpp
+++ b/tests/sys_shm_test.cpp
@@ -52,19 +52,19 @@
   ASSERT_EQ(1234U, ds.shm_segsz);
 
   // Attach.
-  void* p = shmat(id, 0, SHM_RDONLY);
+  void* p = shmat(id, nullptr, SHM_RDONLY);
   ASSERT_NE(p, nullptr);
 
   // Detach.
   ASSERT_EQ(0, shmdt(p));
 
   // Destroy the segment.
-  ASSERT_EQ(0, shmctl(id, IPC_RMID, 0));
+  ASSERT_EQ(0, shmctl(id, IPC_RMID, nullptr));
 }
 
 TEST(sys_shm, shmat_failure) {
   errno = 0;
-  ASSERT_EQ(reinterpret_cast<void*>(-1), shmat(-1, 0, SHM_RDONLY));
+  ASSERT_EQ(reinterpret_cast<void*>(-1), shmat(-1, nullptr, SHM_RDONLY));
   ASSERT_TRUE(errno == EINVAL || errno == ENOSYS);
 }