diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c
index 92ae6acac8a7fbcb9b91cb386b3c23015c5377ea..6aa0f4d9eea6816bbf0c78514e0b76d8f4dc7def 100644
--- a/arch/x86/kernel/tsc_msr.c
+++ b/arch/x86/kernel/tsc_msr.c
@@ -92,7 +92,7 @@ unsigned long try_msr_calibrate_tsc(void)
 
 	if (freq_desc_tables[cpu_index].msr_plat) {
 		rdmsr(MSR_PLATFORM_INFO, lo, hi);
-		ratio = (lo >> 8) & 0x1f;
+		ratio = (lo >> 8) & 0xff;
 	} else {
 		rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 		ratio = (hi >> 8) & 0x1f;