diff --git a/security/pkix/test/lib/pkixtestutil.cpp b/security/pkix/test/lib/pkixtestutil.cpp
index ed5afa524c6c..da0a0be09a37 100644
--- a/security/pkix/test/lib/pkixtestutil.cpp
+++ b/security/pkix/test/lib/pkixtestutil.cpp
@@ -29,7 +29,7 @@
 #include <limits>
 #include <new>
 #include <sstream>
-#include <stdlib.h>
+#include <cstdlib>
 
 #include "pkixder.h"
 #include "pkixutil.h"