diff --git a/configure.ac b/configure.ac
index 735cdfd13..e1bbd1fb8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -61,6 +61,7 @@ AC_PROG_CPP
 AC_PROG_LN_S
 AM_PROG_LIBTOOL
 AC_PROG_YACC
+AM_PROG_LEX
 
 AC_CHECK_LIB(l, main, LEXLIB="-ll", AC_CHECK_LIB(fl, main, LEXLIB="-lfl"))
 AC_SUBST(LEXLIB)