diff --git a/m4/extensions.m4 b/m4/extensions.m4
index 95a54a6f10..58bc0beb6d 100644
--- a/m4/extensions.m4
+++ b/m4/extensions.m4
@@ -1,17 +1,29 @@
+# Enable extensions on systems that normally disable them.
+
+# Copyright (C) 2003 Free Software Foundation, Inc.
+
+# This file is free software, distributed under the terms of the GNU
+# General Public License.  As a special exception to the GNU General
+# Public License, this file may be distributed as part of a program
+# that contains a configuration script generated by Autoconf, under
+# the same distribution terms as the rest of that program.
+
 # gl_USE_SYSTEM_EXTENSIONS
 # ------------------------
 # Enable extensions on systems that normally disable them,
 # typically due to standards-conformance issues.
 AC_DEFUN([gl_USE_SYSTEM_EXTENSIONS], [
-  AC_REQUIRE([AC_AIX])
+  AC_BEFORE([$0], [AC_COMPILE_IFELSE])
+  AC_BEFORE([$0], [AC_RUN_IFELSE])
+
   AC_REQUIRE([AC_GNU_SOURCE])
+  AC_REQUIRE([AC_AIX])
   AC_REQUIRE([AC_MINIX])
+
   AH_VERBATIM([__EXTENSIONS__],
 [/* Enable extensions on Solaris.  */
 #ifndef __EXTENSIONS__
 # undef __EXTENSIONS__
 #endif])
-  AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
-  AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
   AC_DEFINE([__EXTENSIONS__])
 ])