diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -1691,6 +1691,12 @@
 				goto again;
 			}
 			return (error);
+		case ENOTSUP:
+			if (tso && (flags & TH_CWR)) {
+			    tso = 0;
+			    goto send;
+			}
+			return (error);
 		case EHOSTDOWN:
 		case EHOSTUNREACH:
 		case ENETDOWN: