diff --git a/VAX/vax780_bug_history.txt b/VAX/vax780_bug_history.txt
index 8023eb09..b4f32f44 100644
--- a/VAX/vax780_bug_history.txt
+++ b/VAX/vax780_bug_history.txt
@@ -60,6 +60,8 @@ Bugs Found And Fixed During Simulator Debug
 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.
+60. REI to compatibility mode: PSL<dv,fu,iv> were not checked for mbz.
+