diff --git a/VAX/vax780_bug_history.txt b/VAX/vax780_bug_history.txt
index ff6a7e31..8023eb09 100644
--- a/VAX/vax780_bug_history.txt
+++ b/VAX/vax780_bug_history.txt
@@ -59,6 +59,8 @@ Bugs Found And Fixed During Simulator Debug
 56. EMODx: integer overflow case requiring left shift returns wrong result.
 57. BPT, XFC: not clearing PSL<tp> before taking exception.
 58. POLYx: add step <does> require truncation (proved by AXE tests).
+59. Unaligned references to IO space: incorrect on CVAX.
+