diff --git a/src/or/connection.c b/src/or/connection.c
index 791fd95c27..4f636eeb8c 100644
--- a/src/or/connection.c
+++ b/src/or/connection.c
@@ -3581,6 +3581,10 @@ connection_read_to_buf(connection_t *conn, ssize_t *max_to_read,
     if (conn->linked_conn) {
       result = move_buf_to_buf(conn->inbuf, conn->linked_conn->outbuf,
                                &conn->linked_conn->outbuf_flushlen);
+      if (BUG(result<0)) {
+        log_warn(LD_BUG, "reading from linked connection buffer failed.");
+        return -1;
+      }
     } else {
       result = 0;
     }