diff --git a/hw/sparc64/niagara.c b/hw/sparc64/niagara.c
index 1211ecb82d..ad5e5945a8 100644
--- a/hw/sparc64/niagara.c
+++ b/hw/sparc64/niagara.c
@@ -137,7 +137,7 @@ static void niagara_init(MachineState *machine)
        outside of the partition RAM */
     if (dinfo) {
         BlockBackend *blk = blk_by_legacy_dinfo(dinfo);
-        int size = blk_getlength(blk);
+        int64_t size = blk_getlength(blk);
         if (size > 0) {
             memory_region_init_ram(&s->vdisk_ram, NULL, "sun4v_vdisk.ram", size,
                                    &error_fatal);