diff --git a/service/ptos/arch/amd64/ps/context.c b/service/ptos/arch/amd64/ps/context.c
index f0c9801..fed871d 100644
--- a/service/ptos/arch/amd64/ps/context.c
+++ b/service/ptos/arch/amd64/ps/context.c
@@ -59,10 +59,12 @@ HalContextSwitch(TRAP_FRAME *Frame)
     HalMmuWriteVas(&NextParent->Vas);
 
     /* Update the task state segment with kstack */
-    KStackTop = NextTcb->KStackBase + NextTcb->KStackLength;
-    Tss = Mcb->Tss;
-    Tss->Rsp0Low = KStackTop & 0xFFFFFFFF;
-    Tss->Rsp0High = (KStackTop >> 32) & 0xFFFFFFFF;
+    if (ISSET(NextParent->Flags, PS_USER)) {
+        KStackTop = NextTcb->KStackBase + NextTcb->KStackLength;
+        Tss = Mcb->Tss;
+        Tss->Rsp0Low = KStackTop & 0xFFFFFFFF;
+        Tss->Rsp0High = (KStackTop >> 32) & 0xFFFFFFFF;
+    }
 
     /* Context switch here */
     Kpcr->CurrentThread = NextThread;