diff --git a/x86/cstart.S b/x86/cstart.S
index 1714986..5288252 100644
--- a/x86/cstart.S
+++ b/x86/cstart.S
@@ -138,7 +138,7 @@
 	mov %eax, %cr0
 	ret
 
-smp_stacktop:	.long 0xa0000
+smp_stacktop:	.long stacktop - 4096
 
 save_id:
 	movl $(APIC_DEFAULT_PHYS_BASE + APIC_ID), %eax