diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 32e930c853bba4..8b8ecd65c28c42 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -153,7 +153,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
 				const __u64 allowed_access)
 {
 	int ret = 1;
-	char *env_port_name, *strport;
+	char *env_port_name, *env_port_name_next, *strport;
 	struct landlock_net_port_attr net_port = {
 		.allowed_access = allowed_access,
 		.port = 0,
@@ -165,7 +165,8 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
 	env_port_name = strdup(env_port_name);
 	unsetenv(env_var);
 
-	while ((strport = strsep(&env_port_name, ENV_DELIMITER))) {
+	env_port_name_next = env_port_name;
+	while ((strport = strsep(&env_port_name_next, ENV_DELIMITER))) {
 		net_port.port = atoi(strport);
 		if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
 				      &net_port, 0)) {