diff --git a/qmp-commands.hx b/qmp-commands.hx
index 793cf1c..16bdb08 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -495,7 +495,7 @@ EQMP
 
     {
         .name       = "migrate_set_speed",
-        .args_type  = "value:f",
+        .args_type  = "value:o",
         .params     = "value",
         .help       = "set maximum speed (in bytes) for migrations",
         .user_print = monitor_user_noop,