configure.ac | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure.ac b/configure.ac
index 832edec..b035dee 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,6 +67,8 @@ fi
 
 AM_CONFIG_HEADER([src/config.h])
 
+AC_SUBST(CPPFLAGS)
+
 AC_CONFIG_FILES([
 Makefile
 po/Makefile.in