diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index 0e82719..9c2a132 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -1002,7 +1002,7 @@
     case 0x1:
         timer_mod(ppc40x_timer->wdt_timer, next);
         ppc40x_timer->wdt_next = next;
-        env->spr[SPR_40x_TSR] |= 1 << 31;
+        env->spr[SPR_40x_TSR] |= 1U << 31;
         break;
     case 0x2:
         timer_mod(ppc40x_timer->wdt_timer, next);