diff --git a/src/connection.c b/src/connection.c
index 0029b4dd2..0a87eb7cf 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -334,25 +334,45 @@ int conn_unsubscribe(struct connection *conn, void *xprt_ctx, int event_type, st
 	return 0;
 }
 
-/* Called from the upper layer, to unsubscribe <es> from events <event_type>
- * (undo fcgi_subscribe). The <es> struct is not allowed to differ from the one
- * passed to the subscribe() call. It always returns zero.
+/* Called from the upper layer, to subscribe <es> to events <event_type>.
+ * The <es> struct is not allowed to differ from the one passed during a
+ * previous call to subscribe(). If the FD is ready, the wait_event is
+ * immediately woken up and the subcription is cancelled. It always
+ * returns zero.
  */
 int conn_subscribe(struct connection *conn, void *xprt_ctx, int event_type, struct wait_event *es)
 {
 	BUG_ON(event_type & ~(SUB_RETRY_SEND|SUB_RETRY_RECV));
-	BUG_ON(conn->subs && conn->subs->events & event_type);
 	BUG_ON(conn->subs && conn->subs != es);
 
+	if (conn->subs && (conn->subs->events & event_type) == event_type)
+		return 0;
+
 	conn->subs = es;
 	es->events |= event_type;
 
 	if (conn_ctrl_ready(conn)) {
-		if (event_type & SUB_RETRY_RECV)
-			fd_want_recv(conn->handle.fd);
+		if (event_type & SUB_RETRY_RECV) {
+			if (fd_recv_ready(conn->handle.fd)) {
+				tasklet_wakeup(es->tasklet);
+				es->events &= ~SUB_RETRY_RECV;
+				if (!es->events)
+					conn->subs = NULL;
+			}
+			else
+				fd_want_recv(conn->handle.fd);
+		}
 
-		if (event_type & SUB_RETRY_SEND)
-			fd_want_send(conn->handle.fd);
+		if (event_type & SUB_RETRY_SEND) {
+			if (fd_send_ready(conn->handle.fd)) {
+				tasklet_wakeup(es->tasklet);
+				es->events &= ~SUB_RETRY_SEND;
+				if (!es->events)
+					conn->subs = NULL;
+			}
+			else
+				fd_want_send(conn->handle.fd);
+		}
 	}
 	return 0;
 }