diff --git a/configure.ac b/configure.ac
index 345dfc5..668c3bd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -39,7 +39,7 @@ AC_PROG_CC
 AC_PROG_CXX
 AM_PROG_AR
 LT_INIT([shared])
-AC_PROG_LEX(noyywrap)
+AC_PROG_LEX([noyywrap])
 AC_PROG_YACC
 AS_IF([test -z "${LEX}" || test -z "${YACC}"], [
     AC_MSG_ERROR([LEX and YACC must both be available in PATH.])