diff --git a/sys/amd64/include/segments.h b/sys/amd64/include/segments.h
index 1c83d1cf822..8ff3a0f9e27 100644
--- a/sys/amd64/include/segments.h
+++ b/sys/amd64/include/segments.h
@@ -108,12 +108,29 @@ struct	gate_descriptor {
 	u_int64_t sd_xx1:32;
 } __packed;
 
+/*
+ * Generic descriptor
+ */
+union	descriptor	{
+	struct	user_segment_descriptor sd;
+	struct	gate_descriptor gd;
+};
+
 	/* system segments and gate types */
 #define	SDT_SYSNULL	 0	/* system null */
+#define	SDT_SYS286TSS	 1	/* system 286 TSS available */
 #define	SDT_SYSLDT	 2	/* system 64 bit local descriptor table */
+#define	SDT_SYS286BSY	 3	/* system 286 TSS busy */
+#define	SDT_SYS286CGT	 4	/* system 286 call gate */
+#define	SDT_SYSTASKGT	 5	/* system task gate */
+#define	SDT_SYS286IGT	 6	/* system 286 interrupt gate */
+#define	SDT_SYS286TGT	 7	/* system 286 trap gate */
+#define	SDT_SYSNULL2	 8	/* system null again */
 #define	SDT_SYSTSS	 9	/* system available 64 bit TSS */
+#define	SDT_SYSNULL3	10	/* system null again */
 #define	SDT_SYSBSY	11	/* system busy 64 bit TSS */
 #define	SDT_SYSCGT	12	/* system 64 bit call gate */
+#define	SDT_SYSNULL4	13	/* system null again */
 #define	SDT_SYSIGT	14	/* system 64 bit interrupt gate */
 #define	SDT_SYSTGT	15	/* system 64 bit trap gate */