diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c
index 7ede64f..482ed5a 100644
--- a/drivers/lguest/segments.c
+++ b/drivers/lguest/segments.c
@@ -150,7 +150,7 @@
 {
 	/* We assume the Guest has the same number of GDT entries as the
 	 * Host, otherwise we'd have to dynamically allocate the Guest GDT. */
-	if (num > ARRAY_SIZE(cpu->arch.gdt))
+	if (num >= ARRAY_SIZE(cpu->arch.gdt))
 		kill_guest(cpu, "too many gdt entries %i", num);
 
 	/* Set it up, then fix it. */