diff --git a/main.go b/main.go
index b76bbe7..dc0469d 100644
--- a/main.go
+++ b/main.go
@@ -244,6 +244,11 @@ func Main(config *Config, configTest bool, buildVersion string, logger *logrus.L
 
 	amLighthouse := config.GetBool("lighthouse.am_lighthouse", false)
 
+	// fatal if am_lighthouse is enabled but we are using an ephemeral port
+	if amLighthouse && (config.GetInt("listen.port", 0) == 0) {
+		return nil, NewContextualError("lighthouse.am_lighthouse enabled on node but no port number is set in config", nil, nil)
+	}
+
 	// warn if am_lighthouse is enabled but upstream lighthouses exists
 	rawLighthouseHosts := config.GetStringSlice("lighthouse.hosts", []string{})
 	if amLighthouse && len(rawLighthouseHosts) != 0 {