diff --git a/flexnbd.c b/flexnbd.c
index 6286114..56c804c 100644
--- a/flexnbd.c
+++ b/flexnbd.c
@@ -92,6 +92,9 @@ void params_serve(
 	out->bind_to.v4.sin_port = htobe16(out->bind_to.v4.sin_port);
 	
 	out->filename = s_file;
+	out->filename_incomplete = xmalloc(strlen(s_file)+11);
+	strcpy(out->filename_incomplete, s_file);
+	strcpy(out->filename_incomplete + strlen(s_file), ".INCOMPLETE");
 }
 
 void params_readwrite(
diff --git a/params.h b/params.h
index 57df4f4..f0eb55b 100644
--- a/params.h
+++ b/params.h
@@ -38,11 +38,13 @@ struct mode_serve_params {
 	int                  acl_entries;
 	/** pointer to access control list entries*/
 	struct ip_and_mask   (*acl)[0];
-	/** file name to serve */
+	/** (static) file name to serve */
 	char*                filename;
+	/** file name of INCOMPLETE flag */
+	char*                filename_incomplete;
 	/** TCP backlog for listen() */
 	int                  tcp_backlog;
-	/** file name of UNIX control socket (or NULL if none) */
+	/** (static) file name of UNIX control socket (or NULL if none) */
 	char*                control_socket_name;
 	/** size of file */
 	off64_t              size;
diff --git a/readwrite.c b/readwrite.c
index ff1631b..9e006eb 100644
--- a/readwrite.c
+++ b/readwrite.c
@@ -43,9 +43,9 @@ void read_reply(int fd, struct nbd_request *request, struct nbd_reply *reply)
 	SERVER_ERROR_ON_FAILURE(readloop(fd, reply, sizeof(*reply)),
 	  "Couldn't read reply");
 	if (be32toh(reply->magic) != REPLY_MAGIC)
-		SERVER_ERROR("Reply magic incorrect (%p)", reply->magic);
+		SERVER_ERROR("Reply magic incorrect (%p)", be32toh(reply->magic));
 	if (be32toh(reply->error) != 0)
-		SERVER_ERROR("Server replied with error %d", reply->error);
+		SERVER_ERROR("Server replied with error %d", be32toh(reply->error));
 	if (strncmp(request->handle, reply->handle, 8) != 0)
 		SERVER_ERROR("Did not reply with correct handle");
 }
diff --git a/serve.c b/serve.c
index 17408f4..9d1cfb9 100644
--- a/serve.c
+++ b/serve.c
@@ -167,6 +167,12 @@ int client_serve_request(struct client_params* client)
 	switch (be32toh(request.type))
 	{
 	case REQUEST_READ:
+		if (access(client->serve->filename_incomplete, F_OK) == 0 ) {
+			debug("read request while data incomplete");
+			reply.error = htobe32(10);
+			write(client->socket, &reply, sizeof(reply));
+			return 0;
+		}
 	case REQUEST_WRITE:
 		/* check it's not out of range */
 		if (be64toh(request.from) < 0 ||