diff --git a/configure.in b/configure.in
index 045d735..6a6d3a9 100644
--- a/configure.in
+++ b/configure.in
@@ -7,6 +7,7 @@
 AC_PROG_MAKE_SET
 AC_PROG_CC
 AC_PROG_INSTALL
+AM_PROG_LEX
 
 dnl checks for libraries