install-pdf: fix.

[bison.git] / configure.ac

diff --git a/configure.ac b/configure.ac
index 688e18efe74bb137d714af6fc24ea59f616e57ae..704f5aaabc0f37781b4eba34d2b79c766c652bfb 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -114,6 +114,9 @@ AC_SUBST([YACC_LIBRARY])
 
 # Checks for programs.
 AC_PROG_LEX
+if test "$FLEX" != yes; then
+  AC_MSG_ERROR([Flex is required])
+fi
 AC_PROG_YACC
 AC_PROG_RANLIB
 AC_PROG_GNU_M4