test > diff -u mongoc-socket.c mongoc-socket.c.orig 
--- mongoc-socket.c     2019-03-04 16:44:07.000000000 -0600
+++ mongoc-socket.c.orig        2019-03-04 16:41:42.000000000 -0600
@@ -210,11 +210,6 @@
           return (FD_ISSET (sock->sd, &read_fds) ||
                   FD_ISSET (sock->sd, &write_fds));
  #else
- #if defined(_AIX)
-         if (sock->errno_ == ECONNREFUSED) {
-             pfd.revents |= POLLHUP;
-          }
- #endif
           RETURN (0 != (pfd.revents & events));
  #endif
        } else if (ret < 0) {
@@ -342,11 +337,6 @@
     ret = poll (pfds, nsds, timeout);
     for (i = 0; i < nsds; i++) {
        sds[i].revents = pfds[i].revents;
- #if defined(_AIX)
-       if (sds[i].socket->errno_ == ECONNREFUSED) {
-          sds[i].revents |= POLLHUP;
-       }
- #endif
     }
  
     bson_free (pfds);