diff --git a/ChangeLog b/ChangeLog
index ba65266a..5eed423c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2006-11-27  Paul Eggert  <eggert@cs.ucla.edu>
 
+	* doc/autoconf.texi (Setting Output Variables): Mention that
+	@VAR1@VAR2 has unspecified behavior.  Problem reported by
+	Ralf Wildenhues.
+	* NEWS: Mention this.
+
 	* Makefile.am: Put only a single '#' into the copyright notice,
 	so that it's also present in the output file.  Standardize wording
 	in makefile copyright notices to match GNU coding standards.
diff --git a/NEWS b/NEWS
index ca6dc18f..adc5780c 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,10 @@
 * Major changes in Autoconf 2.61a (??)
 
 ** config.status now uses awk instead of sed for most substitutions, for speed.
+   It is now documented that Makefile.in should not contain
+   overlapping variable occurrences, e.g., @VAR1@VAR2@.  Autoconf's
+   behavior was always iffy in such cases, and the awk implementation
+   has changed the behavior.
 
 * Major changes in Autoconf 2.61 (2006-11-17)
 
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index c6618221..a244000a 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -8349,6 +8349,9 @@ or more makefiles).  This means that @code{AC_OUTPUT}
 replaces instances of @samp{@@@var{variable}@@} in input files with the
 value that the shell variable @var{variable} has when @code{AC_OUTPUT}
 is called.  The value can contain newlines.
+Variable occurrences should not overlap: e.g., an input file should
+not contain @samp{@@@var{var1}@@@var{var2}@@} if @var{var1} and @var{var2}
+are variable names.
 The substituted value is not rescanned for more output variables;
 occurrences of @samp{@@@var{variable}@@} in the value are inserted
 literally into the output file.  (The algorithm uses the special marker