diff --git a/bootfiles/20a/boot-2010-06-cross-x86.lisp b/bootfiles/20a/boot-2010-06-cross-x86.lisp
index f47a351957f231c5c64575df4f06baf737818755..bc993a8f0f1446475adf6d134a4bfad67b3d2adb 100644
--- a/bootfiles/20a/boot-2010-06-cross-x86.lisp
+++ b/bootfiles/20a/boot-2010-06-cross-x86.lisp
@@ -1,2 +1,5 @@
+;; Cross-compile script for x86 to add new SC numbers the xmm
+;; (floating-point) registers.  The default cross-compile script is
+;; good enough for this.
 #+x86
 (load "target:tools/cross-scripts/cross-x86-x86")