diff --git a/rmw_zenoh_cpp/src/rmw_zenoh.cpp b/rmw_zenoh_cpp/src/rmw_zenoh.cpp
index f2c4974c..06355e34 100644
--- a/rmw_zenoh_cpp/src/rmw_zenoh.cpp
+++ b/rmw_zenoh_cpp/src/rmw_zenoh.cpp
@@ -1568,7 +1568,7 @@ rmw_destroy_subscription(rmw_node_t * node, rmw_subscription_t * subscription)
     allocator->deallocate(sub_data->type_support, allocator->state);
 
     z_owned_subscriber_t * sub = std::get_if<z_owned_subscriber_t>(&sub_data->sub);
-    if (sub != NULL) {
+    if (sub != nullptr) {
       if (z_undeclare_subscriber(z_move(*sub)) != Z_OK) {
         RMW_SET_ERROR_MSG("failed to undeclare sub");
         ret = RMW_RET_ERROR;
@@ -1576,7 +1576,7 @@ rmw_destroy_subscription(rmw_node_t * node, rmw_subscription_t * subscription)
     } else {
       ze_owned_querying_subscriber_t * querying_sub =
         std::get_if<ze_owned_querying_subscriber_t>(&sub_data->sub);
-      if (querying_sub == NULL || ze_undeclare_querying_subscriber(z_move(*querying_sub))) {
+      if (querying_sub == nullptr || ze_undeclare_querying_subscriber(z_move(*querying_sub))) {
         RMW_SET_ERROR_MSG("failed to undeclare sub");
         ret = RMW_RET_ERROR;
       }