diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 386d37a228bb71d7717f46c76d3fc4b7a05ab015..0931b110c8260d30774d1ed3c89acb3e300a44b6 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -226,7 +226,7 @@ void update_vsyscall(struct timekeeper *tk)
 	vdso_data->wtom_clock_sec =
 		tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
 	vdso_data->wtom_clock_nsec = tk->xtime_nsec +
-		+ (tk->wall_to_monotonic.tv_nsec << tk->shift);
+		+ ((u64) tk->wall_to_monotonic.tv_nsec << tk->shift);
 	nsecps = (u64) NSEC_PER_SEC << tk->shift;
 	while (vdso_data->wtom_clock_nsec >= nsecps) {
 		vdso_data->wtom_clock_nsec -= nsecps;