diff --git a/backends/hostmem.c b/backends/hostmem.c
index a70867b..327f9ee 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -280,6 +280,7 @@
     /* TODO: convert access to globals to compat properties */
     backend->merge = machine_mem_merge(machine);
     backend->dump = machine_dump_guest_core(machine);
+    backend->prealloc_threads = 1;
 }
 
 static void host_memory_backend_post_init(Object *obj)