diff --git a/libc/bionic/brk.cpp b/libc/bionic/brk.cpp
index e1a4b05..566c33a 100644
--- a/libc/bionic/brk.cpp
+++ b/libc/bionic/brk.cpp
@@ -48,8 +48,8 @@
 
 void* sbrk(ptrdiff_t increment) {
   // Initialize __bionic_brk if necessary.
-  if (__bionic_brk == NULL) {
-    __bionic_brk = __brk(NULL);
+  if (__bionic_brk == nullptr) {
+    __bionic_brk = __brk(nullptr);
   }
 
   // Don't ask the kernel if we already know the answer.