diff --git a/configure.ac b/configure.ac
index d83b5ec50e..f46d80df4f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1325,8 +1325,8 @@ AX_CHECK_COMPILE_FLAG([-Wno-deprecated-register],
     [AM_CXXFLAGS="${AM_CXXFLAGS} -Wno-unused -Wno-deprecated-register"],
     [AM_CXXFLAGS="${AM_CXXFLAGS} -Wno-unused"], [-Werror])
 AC_LANG([C])
-AX_CHECK_COMPILE_FLAG([-Wno-non-literal-null-conversion],
-    [AM_CFLAGS="${AM_CFLAGS} -Wno-non-literal-null-conversion"],
+AX_CHECK_PREPROC_FLAG([-Wno-non-literal-null-conversion],
+    [AM_CPPFLAGS="${AM_CPPFLAGS} -Wno-non-literal-null-conversion"],
     [], [-Werror])
 AC_MSG_CHECKING(what extra warning flags to pass to the C compiler)
 if test ${GCC}x = yesx
diff --git a/macros/ax_check_preproc_flag.m4 b/macros/ax_check_preproc_flag.m4
new file mode 100644
index 0000000000..9a1d5c93db
--- /dev/null
+++ b/macros/ax_check_preproc_flag.m4
@@ -0,0 +1,74 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_check_preproc_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_PREPROC_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the current language's
+#   preprocessor or gives an error.  (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the preprocessor's default
+#   flags when the check is done.  The check is thus made with the flags:
+#   "CPPFLAGS EXTRA-FLAGS FLAG".  This can for example be used to force the
+#   preprocessor to issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_PREPROC_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{COMPILE,LINK}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 3
+
+AC_DEFUN([AX_CHECK_PREPROC_FLAG],
+[AC_PREREQ(2.59)dnl for _AC_LANG_PREFIX
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]cppflags_$4_$1])dnl
+AC_CACHE_CHECK([whether _AC_LANG preprocessor accepts $1], CACHEVAR, [
+  ax_check_save_flags=$CPPFLAGS
+  CPPFLAGS="$CPPFLAGS $4 $1"
+  AC_PREPROC_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  CPPFLAGS=$ax_check_save_flags])
+AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes],
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_PREPROC_FLAGS