diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 3ff09a26e67..8a90db4c6d9 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2008-07-30  Thien-Thi Nguyen  <ttn@gnuvola.org>
+
+	* info-look.el (autoconf-mode :doc-spec): For
+	"(autoconf)M4 Macro Index", if the item already
+	begins with "AS_", don't prefix that string again.
+
 2008-07-30  Juri Linkov  <juri@jurta.org>
 
 	* info.el (info, Info-mode): Doc fix.
diff --git a/lisp/info-look.el b/lisp/info-look.el
index e7ac5bd0d54..fc8ff1e578b 100644
--- a/lisp/info-look.el
+++ b/lisp/info-look.el
@@ -755,12 +755,15 @@ Return nil if there is nothing appropriate in the buffer near point."
              ;; M4 Macro Index entries are without "AS_" prefixes, and
              ;; mostly without "m4_" prefixes.  "dnl" is an exception, not
              ;; wanting any prefix.  So AS_ is added back to upper-case
-             ;; names, m4_ to others which don't already an m4_.
+             ;; names (if needed), m4_ to others which don't already an m4_.
              ("(autoconf)M4 Macro Index"
               (lambda (item)
                 (let ((case-fold-search nil))
                   (cond ((or (string-equal item "dnl")
-                             (string-match "^m4_" item))
+                             (string-match "^m4_" item)
+                             ;; Autoconf 2.62 index includes some macros
+                             ;; (e.g., AS_HELP_STRING), so avoid prefixing.
+                             (string-match "^AS_" item))
                          item)
                         ((string-match "^[A-Z0-9_]+$" item)
                          (concat "AS_" item))