diff --git a/xtoskrnl/ar/amd64/procsup.c b/xtoskrnl/ar/amd64/procsup.c
index cc7fe95..2239aad 100644
--- a/xtoskrnl/ar/amd64/procsup.c
+++ b/xtoskrnl/ar/amd64/procsup.c
@@ -216,7 +216,7 @@ ArpInitializeGdt(IN PKPROCESSOR_BLOCK ProcessorBlock)
     ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_R3_CMCODE, 0x0, 0xFFFFFFFF, KGDT_TYPE_CODE, KGDT_DPL_USER, 2);
     ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_R3_DATA, 0x0, 0xFFFFFFFF, KGDT_TYPE_DATA, KGDT_DPL_USER, 2);
     ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_R3_CODE, 0x0, 0x0, KGDT_TYPE_CODE, KGDT_DPL_USER, 1);
-    ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_SYS_TSS, (ULONG_PTR)ProcessorBlock->TssBase, sizeof(KTSS), AMD64_TSS, KGDT_DPL_SYSTEM, 0);
+    ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_SYS_TSS, (ULONG_PTR)ProcessorBlock->TssBase, sizeof(KTSS) - 1, AMD64_TSS, KGDT_DPL_SYSTEM, 0);
     ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_R3_CMTEB, 0x0, 0x0FFF, KGDT_TYPE_DATA, KGDT_DPL_USER, 2);
     ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_R0_LDT, 0x0, 0xFFFFFFFF, KGDT_TYPE_CODE, KGDT_DPL_SYSTEM, 0);
     ArpSetGdtEntry(ProcessorBlock->GdtBase, KGDT_ALIAS, (ULONG_PTR)ProcessorBlock->GdtBase, (GDT_ENTRIES * sizeof(KGDTENTRY)) - 1, KGDT_TYPE_DATA, KGDT_DPL_SYSTEM, 0);