diff --git a/Makefile.am b/Makefile.am
index 7af3b79..545e69b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -8,7 +8,7 @@ pkg_default_dir        = @PKG_DEFAULT_PATH@
 pkgconfigdir           = $(libdir)/pkgconfig
 nodist_pkgconfig_DATA  = libpkgconf.pc
 
-AM_CFLAGS = -Wall -Wextra -Wformat=2 -std=gnu99 -DPKG_DEFAULT_PATH=\"$(pkg_default_dir)\" -DSYSTEM_INCLUDEDIR=\"$(system_includedir)\" -DSYSTEM_LIBDIR=\"$(system_libdir)\"
+AM_CFLAGS = -DPKG_DEFAULT_PATH=\"$(pkg_default_dir)\" -DSYSTEM_INCLUDEDIR=\"$(system_includedir)\" -DSYSTEM_LIBDIR=\"$(system_libdir)\"
 
 bin_PROGRAMS = pkgconf
 lib_LTLIBRARIES = libpkgconf.la
diff --git a/configure.ac b/configure.ac
index 2f284eb..ec67603 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,6 +14,12 @@ dnl from the use of this software.
 AC_PREREQ([2.68])
 AC_INIT([pkgconf], [1.3.7], [http://github.com/pkgconf/pkgconf/issues])
 AC_CONFIG_SRCDIR([main.c])
+AX_CHECK_COMPILE_FLAG([-Wall], [CFLAGS="$CFLAGS -Wall"])
+AX_CHECK_COMPILE_FLAG([-Wextra], [CFLAGS="$CFLAGS -Wextra"])
+AX_CHECK_COMPILE_FLAG([-Wformat=2], [CFLAGS="$CFLAGS -Wformat=2"])
+AX_CHECK_COMPILE_FLAG([-std=gnu99], [CFLAGS="$CFLAGS -std=gnu99"], [
+	AX_CHECK_COMPILE_FLAG([-std=c99], [CFLAGS="$CFLAGS -std=c99"])
+])
 AC_CONFIG_HEADERS([libpkgconf/config.h])
 AC_CHECK_FUNCS([strlcpy strlcat strndup cygwin_conv_path])
 AC_CHECK_HEADERS([sys/stat.h])