diff --git a/extent_writer_unittest.cc b/extent_writer_unittest.cc
index fcd57dd..fef3343 100644
--- a/extent_writer_unittest.cc
+++ b/extent_writer_unittest.cc
@@ -92,7 +92,7 @@
 
   DirectExtentWriter direct_writer;
   EXPECT_TRUE(direct_writer.Init(fd(), extents, kBlockSize));
-  EXPECT_TRUE(direct_writer.Write(NULL, 0));
+  EXPECT_TRUE(direct_writer.Write(nullptr, 0));
   EXPECT_TRUE(direct_writer.End());
 }