diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index ecef63f..caeb539 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -146,6 +146,9 @@
 			if (flags & 2)
 				((struct sockaddr_in6 *)&bind_addr)->sin6_port = ((struct sockaddr_in6 *)remote)->sin6_port;
 			break;
+		default:
+			/* we don't want to try to bind to an unknown address family */
+			foreign_ok = 0;
 		}
 	}