diff --git a/lib/cpp/test/RecursiveTest.cpp b/lib/cpp/test/RecursiveTest.cpp
index 15f234c..ab2e46d 100644
--- a/lib/cpp/test/RecursiveTest.cpp
+++ b/lib/cpp/test/RecursiveTest.cpp
@@ -60,8 +60,8 @@
 
   RecList resultlist;
   resultlist.read(prot.get());
-  BOOST_CHECK(resultlist.nextitem != NULL);
-  BOOST_CHECK(resultlist.nextitem->nextitem == NULL);
+  BOOST_CHECK(resultlist.nextitem != nullptr);
+  BOOST_CHECK(resultlist.nextitem->nextitem == nullptr);
 }
 
 BOOST_AUTO_TEST_CASE(test_recursive_3) {
@@ -75,8 +75,8 @@
   c.write(prot.get());
 
   c.read(prot.get());
-  BOOST_CHECK(c.other != NULL);
-  BOOST_CHECK(c.other->other.other == NULL);
+  BOOST_CHECK(c.other != nullptr);
+  BOOST_CHECK(c.other->other.other == nullptr);
 }
 
 BOOST_AUTO_TEST_CASE(test_recursive_4) {