diff --git a/file_writer_unittest.cc b/file_writer_unittest.cc
index 5d24eab..8f4ab9e 100644
--- a/file_writer_unittest.cc
+++ b/file_writer_unittest.cc
@@ -26,7 +26,7 @@
 TEST(FileWriterTest, SimpleTest) {
   // Create a uniquely named file for testing.
   string path;
-  ASSERT_TRUE(utils::MakeTempFile("FileWriterTest-XXXXXX", &path, NULL));
+  ASSERT_TRUE(utils::MakeTempFile("FileWriterTest-XXXXXX", &path, nullptr));
   ScopedPathUnlinker path_unlinker(path);
 
   DirectFileWriter file_writer;
@@ -51,7 +51,7 @@
 TEST(FileWriterTest, WriteErrorTest) {
   // Create a uniquely named file for testing.
   string path;
-  ASSERT_TRUE(utils::MakeTempFile("FileWriterTest-XXXXXX", &path, NULL));
+  ASSERT_TRUE(utils::MakeTempFile("FileWriterTest-XXXXXX", &path, nullptr));
   ScopedPathUnlinker path_unlinker(path);
 
   DirectFileWriter file_writer;