diff --git a/tests/semaphore_test.cpp b/tests/semaphore_test.cpp
index 607e37f..10d99ea 100644
--- a/tests/semaphore_test.cpp
+++ b/tests/semaphore_test.cpp
@@ -78,9 +78,9 @@
   ASSERT_EQ(0, sem_init(&s, 0, 0));
 
   pthread_t t1, t2, t3;
-  ASSERT_EQ(0, pthread_create(&t1, NULL, SemWaitThreadFn, &s));
-  ASSERT_EQ(0, pthread_create(&t2, NULL, SemWaitThreadFn, &s));
-  ASSERT_EQ(0, pthread_create(&t3, NULL, SemWaitThreadFn, &s));
+  ASSERT_EQ(0, pthread_create(&t1, nullptr, SemWaitThreadFn, &s));
+  ASSERT_EQ(0, pthread_create(&t2, nullptr, SemWaitThreadFn, &s));
+  ASSERT_EQ(0, pthread_create(&t3, nullptr, SemWaitThreadFn, &s));
 
   ASSERT_EQ(0, sem_post(&s));
   ASSERT_EQ(0, sem_post(&s));