diff --git a/kernel/kernel.asm b/kernel/kernel.asm
index e51a2d3..89d7520 100644
--- a/kernel/kernel.asm
+++ b/kernel/kernel.asm
@@ -581,7 +581,7 @@ _CritPatch      dw      0               ;-11 zero list of patched critical
                 dw      0               ;    DOS puts 0d0ch here but some
                 dw      0               ;    progs really write to that addr.
                 dw      0               ;-03 - critical patch list terminator
-                db      0               ;-01 - unknown
+                db      90h             ;-01 - unused, NOP pad byte
 _internal_data:              ; <-- Address returned by INT21/5D06
 _ErrorMode      db      0               ; 00 - Critical Error Flag
 _InDOS          db      0               ; 01 - Indos Flag