diff --git a/acl-scanner.l b/acl-scanner.l
index ea5f1a7..a9d3c43 100644
--- a/acl-scanner.l
+++ b/acl-scanner.l
@@ -18,6 +18,7 @@
  * this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "config.h"
 #include <ctype.h>
 #define YY_NO_INPUT
 #include "acl-parser.h"