diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index cde2a16b94..39d37e1225 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -838,6 +838,7 @@ typedef uint64_t FeatureWordArray[FEATURE_WORDS];
 #define MSR_ARCH_CAP_RSBA       (1U << 2)
 #define MSR_ARCH_CAP_SKIP_L1DFL_VMENTRY (1U << 3)
 #define MSR_ARCH_CAP_SSB_NO     (1U << 4)
+#define MSR_ARCH_CAP_MDS_NO     (1U << 5)
 
 #define MSR_CORE_CAP_SPLIT_LOCK_DETECT  (1U << 5)