--- info-look.el.orig	2011-05-12 08:36:49.000000000 +1000
+++ info-look.el	2011-05-12 10:13:37.000000000 +1000
@@ -720,11 +720,44 @@
  :mode 'makefile-mode
  :regexp "\\$[^({]\\|\\.[_A-Z]*\\|[_a-zA-Z][_a-zA-Z0-9-]*"
  :doc-spec '(("(make)Name Index" nil
-	      "^[ \t]*`" "'")
-	     ("(automake)Macro and Variable Index" nil
 	      "^[ \t]*`" "'"))
- :parse-rule "\\$[^({]\\|\\.[_A-Z]*\\|[_a-zA-Z0-9-]+"
- :other-modes '(automake-mode))
+ :parse-rule "\\$[^({]\\|\\.[_A-Z]*\\|[_a-zA-Z0-9-]+")
+
+(info-lookup-maybe-add-help
+ :topic      'symbol
+ :mode       'makefile-automake-mode
+ ;; similar regexp/parse-rule as makefile-mode, but also
+ ;;   "##" special automake comment
+ ;;   "+=" append operator, separate from the GNU make one
+ :regexp     "\\$[^({]\\|\\.[_A-Z]*\\|[_a-zA-Z][_a-zA-Z0-9-]*\\|##\\|\\+="
+ :parse-rule "\\$[^({]\\|\\.[_A-Z]*\\|[_a-zA-Z0-9-]+\\|##\\|\\+="
+ :doc-spec   '(
+               ;; "(automake)Macro Index" is autoconf macros used in
+               ;; configure.in, not Makefile.am, so don't have that here.
+               ("(automake)Variable Index" nil "^[ \t]*`" "'")
+               ;; In automake 1.4 macros and variables were a combined node.
+               ("(automake)Macro and Variable Index" nil "^[ \t]*`" "'")
+               ;; Directives like "if" are in the "General Index".
+               ;; Prefix "`" since the text for say `+=' isn't always an
+               ;; @item etc and so not always at the start of a line.
+               ("(automake)General Index" nil "`" "'")
+               ;; In automake 1.3 there was just a single "Index" node.
+               ("(automake)Index" nil "`" "'"))
+ :other-modes '(makefile-mode))
+
+;; makefile-mode derivatives going to plain makefile-mode.
+(let ((regexp     (info-lookup->regexp     'symbol 'makefile-mode))
+      (parse-rule (info-lookup->parse-rule 'symbol 'makefile-mode)))
+  (dolist (mode '(makefile-bsdmake-mode
+                  makefile-gmake-mode
+                  makefile-imake-mode
+                  makefile-makepp-mode))
+    (info-lookup-maybe-add-help
+     :topic       'symbol
+     :mode        mode
+     :regexp      regexp
+     :parse-rule  parse-rule
+     :other-modes '(makefile-mode))))
 
 (info-lookup-maybe-add-help
  :mode 'texinfo-mode