diff --git a/hw/ssi/aspeed_smc.c b/hw/ssi/aspeed_smc.c
index 68aa697164..faed7e0cbe 100644
--- a/hw/ssi/aspeed_smc.c
+++ b/hw/ssi/aspeed_smc.c
@@ -488,7 +488,7 @@ static uint64_t aspeed_smc_flash_read(void *opaque, hwaddr addr, unsigned size)
     switch (aspeed_smc_flash_mode(fl)) {
     case CTRL_USERMODE:
         for (i = 0; i < size; i++) {
-            ret |= ssi_transfer(s->spi, 0x0) << (8 * i);
+            ret |= (uint64_t) ssi_transfer(s->spi, 0x0) << (8 * i);
         }
         break;
     case CTRL_READMODE:
@@ -497,7 +497,7 @@ static uint64_t aspeed_smc_flash_read(void *opaque, hwaddr addr, unsigned size)
         aspeed_smc_flash_setup(fl, addr);
 
         for (i = 0; i < size; i++) {
-            ret |= ssi_transfer(s->spi, 0x0) << (8 * i);
+            ret |= (uint64_t) ssi_transfer(s->spi, 0x0) << (8 * i);
         }
 
         aspeed_smc_flash_unselect(fl);