diff --git a/nbd/client.c b/nbd/client.c
index 7f35b5c323..232ff4f46d 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -435,8 +435,8 @@ static int nbd_opt_go(QIOChannel *ioc, const char *wantname,
             }
             be32_to_cpus(&info->min_block);
             if (!is_power_of_2(info->min_block)) {
-                error_setg(errp, "server minimum block size %" PRId32
-                           "is not a power of two", info->min_block);
+                error_setg(errp, "server minimum block size %" PRIu32
+                           " is not a power of two", info->min_block);
                 nbd_send_opt_abort(ioc);
                 return -1;
             }
@@ -450,8 +450,8 @@ static int nbd_opt_go(QIOChannel *ioc, const char *wantname,
             be32_to_cpus(&info->opt_block);
             if (!is_power_of_2(info->opt_block) ||
                 info->opt_block < info->min_block) {
-                error_setg(errp, "server preferred block size %" PRId32
-                           "is not valid", info->opt_block);
+                error_setg(errp, "server preferred block size %" PRIu32
+                           " is not valid", info->opt_block);
                 nbd_send_opt_abort(ioc);
                 return -1;
             }
@@ -462,6 +462,12 @@ static int nbd_opt_go(QIOChannel *ioc, const char *wantname,
                 return -1;
             }
             be32_to_cpus(&info->max_block);
+            if (info->max_block < info->min_block) {
+                error_setg(errp, "server maximum block size %" PRIu32
+                           " is not valid", info->max_block);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
             trace_nbd_opt_go_info_block_size(info->min_block, info->opt_block,
                                              info->max_block);
             break;