diff --git a/ChangeLog b/ChangeLog
index b7f8f77dd34..b1d1d65c667 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2011-04-07  Glenn Morris  <rgm@gnu.org>
+
+	* autogen/update_autogen: Ignore comment diffs in ldefs-boot.el.
+
 2011-04-06  Eli Zaretskii  <eliz@gnu.org>
 
 	* lib/makefile.w32-in ($(BLD)/careadlinkat.$(O), GNULIBOBJS):
diff --git a/autogen/update_autogen b/autogen/update_autogen
index d1687b293e9..c134609356c 100755
--- a/autogen/update_autogen
+++ b/autogen/update_autogen
@@ -268,7 +268,10 @@ echo "Running lisp/ make..."
 make -C lisp "$@" autoloads EMACS=../src/bootstrap-emacs || die "make src error"
 
 
-[ ! "$lboot_flag" ] || cp $ldefs_in $ldefs_out || die "cp ldefs_boot error"
+## Ignore comment differences.
+[ ! "$lboot_flag" ] || \
+    diff -q -I '^;' $ldefs_in $ldefs_out || \
+    cp $ldefs_in $ldefs_out || die "cp ldefs_boot error"
 
 
 cd lisp