diff --git a/vmmon-only/include/x86msr.h b/vmmon-only/include/x86msr.h
index 63f2213..cf9a976 100644
--- a/vmmon-only/include/x86msr.h
+++ b/vmmon-only/include/x86msr.h
@@ -453,7 +453,9 @@ typedef enum {
 #define MSR_K7_HWCR_SSEDIS         0x00008000ULL // Disable SSE bit
 #define MSR_K7_HWCR_MONMWAITUSEREN 0x00000400ULL // Enable MONITOR/MWAIT CPL>0
 #define MSR_K7_HWCR_TLBFFDIS       0x00000040ULL // Disable TLB Flush Filter
+#ifndef MSR_K7_HWCR_SMMLOCK
 #define MSR_K7_HWCR_SMMLOCK        0x00000001ULL // Lock SMM environment
+#endif
 
 #ifndef MSR_K8_SYSCFG
 #define MSR_K8_SYSCFG        0xc0010010