diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 841654562d76..2533c0b06d5b 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -1771,6 +1771,8 @@ pmap_bootstrap(vm_paddr_t *firstaddr)
 	pcpu_init(&__pcpu[0], 0, sizeof(struct pcpu));
 	amd64_bsp_pcpu_init1(&__pcpu[0]);
 	amd64_bsp_ist_init(&__pcpu[0]);
+	__pcpu[0].pc_common_tss.tss_iobase = sizeof(struct amd64tss) +
+	    IOPERM_BITMAP_SIZE;
 	memcpy(__pcpu[0].pc_gdt, temp_bsp_pcpu.pc_gdt, NGDT *
 	    sizeof(struct user_segment_descriptor));
 	gdt_segs[GPROC0_SEL].ssd_base = (uintptr_t)&__pcpu[0].pc_common_tss;