diff --git a/slirp/socket.c b/slirp/socket.c
index 7c8af778..eebe282e 100644
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -93,12 +93,14 @@ size_t sopreprbuf(struct socket *so, struct iovec *iov, int *np)
         DEBUG_CALL("sopreprbuf");
         DEBUG_ARG("so = %lx", (long )so);
 
-        if (len <= 0)
-                return 0;
-
         iov[0].iov_base = sb->sb_wptr;
         iov[1].iov_base = NULL;
         iov[1].iov_len = 0;
+        if (np)
+                *np = 1;
+        if (len <= 0)
+                return 0;
+
         if (sb->sb_wptr < sb->sb_rptr) {
                 iov[0].iov_len = sb->sb_rptr - sb->sb_wptr;
                 /* Should never succeed, but... */