diff --git a/changes/bug2430 b/changes/bug2430
new file mode 100644
index 0000000000..3908856b3d
--- /dev/null
+++ b/changes/bug2430
@@ -0,0 +1,4 @@
+  o Minor bugfixes:
+    - Fix a bug in configure.in that kept it from building a configure
+      script with autoconf versions earlier than 2.61. Fixes bug 2430;
+      bugfix on 0.2.3.1-alpha.
diff --git a/configure.in b/configure.in
index a449136f93..c6ee589987 100644
--- a/configure.in
+++ b/configure.in
@@ -189,9 +189,9 @@ AC_C_FLEXIBLE_ARRAY_MEMBER
   [tor_cv_c_flexarray=yes],
   [tor_cv_c_flexarray=no])])
  if test $tor_cv_flexarray = yes ; then
-   AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [])
+   AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [], [Define to nothing if C supports flexible array members, and to 1 if it does not.])
  else
-   AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [1])
+   AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [1], [Define to nothing if C supports flexible array members, and to 1 if it does not.])
  fi
 ])