diff --git a/headers/private/kernel/arch/x86/arch_cpu.h b/headers/private/kernel/arch/x86/arch_cpu.h
index abdbb862d6..7f1731f645 100644
--- a/headers/private/kernel/arch/x86/arch_cpu.h
+++ b/headers/private/kernel/arch/x86/arch_cpu.h
@@ -49,8 +49,6 @@
 #define IA32_MSR_MTRR_PHYSICAL_BASE_0	0x200
 #define IA32_MSR_MTRR_PHYSICAL_MASK_0	0x201
 
-#define IA32_MSR_EFER					0xc0000080
-
 
 // MSR APIC BASE bits
 #define IA32_MSR_APIC_BASE_BSP			0x00000100
@@ -86,8 +84,10 @@
 #define IA32_MSR_XSS						0x00000da0
 
 // x86_64 MSRs.
+#define IA32_MSR_EFER					0xc0000080
 #define IA32_MSR_STAR					0xc0000081
 #define IA32_MSR_LSTAR					0xc0000082
+#define IA32_MSR_CSTAR					0xc0000083
 #define IA32_MSR_FMASK					0xc0000084
 #define IA32_MSR_FS_BASE				0xc0000100
 #define IA32_MSR_GS_BASE				0xc0000101