Index: kernel/arch/ia32/src/proc/scheduler.c
===================================================================
--- kernel/arch/ia32/src/proc/scheduler.c	(revision 99d6fd07a4e12eb667d2cfa2d3fdb3b5f63800b2)
+++ kernel/arch/ia32/src/proc/scheduler.c	(revision 3cc110fd26aa526528a9c7a4962a95fc10e58feb)
@@ -61,6 +61,8 @@
 	    SP_DELTA];
 	
-	/* Set kernel stack for CP3 -> CPL0 switch via SYSENTER */
-	write_msr(IA32_MSR_SYSENTER_ESP, kstk);
+	if (CPU->arch.fi.bits.sep) {
+		/* Set kernel stack for CP3 -> CPL0 switch via SYSENTER */
+		write_msr(IA32_MSR_SYSENTER_ESP, kstk);
+	}
 	
 	/* Set kernel stack for CPL3 -> CPL0 switch via interrupt */