diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 0e8812a11d..9f69d7e192 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -339,7 +339,7 @@ static const ExtSaveArea ext_save_areas[] = {
     [3] = { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_MPX,
             .offset = 0x3c0, .size = 0x40  },
     [4] = { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_MPX,
-            .offset = 0x400, .size = 0x10  },
+            .offset = 0x400, .size = 0x40  },
 };
 
 const char *get_register_name_32(unsigned int reg)