diff --git a/src/main.cpp b/src/main.cpp
index c30c786..4c7cb84 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -63,7 +63,7 @@ int main(int argc, char *argv[]) {
 	char *res_loc;
 	switch (argc - optind) {
 	case 0: {
-		res_loc = NULL;
+		res_loc = nullptr;
 		for (const auto& fe : std::filesystem::directory_iterator(".")) {
 			if (!fe.is_regular_file())
 				continue;
@@ -72,9 +72,9 @@ int main(int argc, char *argv[]) {
 			if (fp.extension() != ".shp")
 				continue;
 
-			if (res_loc != NULL) {
+			if (res_loc != nullptr) {
 				free(res_loc);
-				res_loc = NULL;
+				res_loc = nullptr;
 				break;
 			}
 
@@ -83,7 +83,7 @@ int main(int argc, char *argv[]) {
 			fps.copy(res_loc, fps.size());
 			res_loc[fps.size()] = '\0';
 		}
-		if (res_loc == NULL) {
+		if (res_loc == nullptr) {
 			std::cerr << "Failed to automatically find residents shapefile!" << std::endl;
 			return 1;
 		}