diff --git a/src/charon-nm/charon-nm.c b/src/charon-nm/charon-nm.c
index 0134f5a71..1aa975efb 100644
--- a/src/charon-nm/charon-nm.c
+++ b/src/charon-nm/charon-nm.c
@@ -196,9 +196,9 @@ int main(int argc, char *argv[])
 							   "charon-nm.syslog.daemon.default", 1));
 	charon->load_loggers(charon);
 
-	/* use random ports to avoid conflicts with regular charon */
-	lib->settings->set_int(lib->settings, "charon-nm.port", 0);
-	lib->settings->set_int(lib->settings, "charon-nm.port_nat_t", 0);
+	/* default to random ports to avoid conflicts with regular charon */
+	lib->settings->set_default_str(lib->settings, "charon-nm.port", "0");
+	lib->settings->set_default_str(lib->settings, "charon-nm.port_nat_t", "0");
 
 	DBG1(DBG_DMN, "Starting charon NetworkManager backend (strongSwan "VERSION")");
 	if (lib->integrity)