diff --git a/src/iodined.c b/src/iodined.c
index 0d4694d..3b4652c 100644
--- a/src/iodined.c
+++ b/src/iodined.c
@@ -495,10 +495,6 @@ main(int argc, char **argv)
 			break;
 		case 'p':
 			port = atoi(optarg);
-			if (port) {
-				printf("ALERT! Other dns servers expect you to run on port 53.\n");
-				printf("You must manually forward port 53 to port %d for things to work.\n", port);
-			}
 			break;
 		case 'P':
 			strncpy(password, optarg, sizeof(password));
@@ -547,6 +543,16 @@ main(int argc, char **argv)
 		warnx("Bad MTU given.\n");
 		usage();
 	}
+	
+	if(port < 1 || port > 65535) {
+		warnx("Bad port number given.\n");
+		usage();
+	}
+	
+	if (port != 53) {
+		printf("ALERT! Other dns servers expect you to run on port 53.\n");
+		printf("You must manually forward port 53 to port %d for things to work.\n", port);
+	}
 
 	if (listen_ip == INADDR_NONE) {
 		warnx("Bad IP address to listen on.\n");