diff --git a/winnet.c b/winnet.c
index 01b4f1ba..131f00a7 100644
--- a/winnet.c
+++ b/winnet.c
@@ -504,8 +504,15 @@ void try_send(Actual_Socket s) {
         noise_ultralight(nsent);
 	if (nsent <= 0) {
 	    err = (nsent < 0 ? WSAGetLastError() : 0);
-	    if (err == WSAEWOULDBLOCK) {
-		/* Perfectly normal: we've sent all we can for the moment. */
+	    if ((err==0 && nsent < 0) || err == WSAEWOULDBLOCK) {
+		/*
+		 * Perfectly normal: we've sent all we can for the moment.
+		 * 
+		 * (Apparently some WinSocks can return <0 but
+		 * leave no error indication - WSAGetLastError() is
+		 * called but returns zero - so we check that case
+		 * and treat it just like WSAEWOULDBLOCK.)
+		 */
 		s->writable = FALSE;
                 return;
 	    } else if (nsent == 0 ||