diff --git a/configure.ac b/configure.ac
index 379b92433..94183a47a 100755
--- a/configure.ac
+++ b/configure.ac
@@ -64,7 +64,7 @@ AC_PROG_MKDIR_P
 AM_PROG_LEX
 # Hack to get lex include dir, ticket #575
 AC_PATH_PROG([LEXPATH], [$LEX])
-AC_SUBST([LEXINC], [`eval "echo $LEXPATH | sed 's|$LEX$|../include|'"`])
+AC_SUBST([LEXINC], [`eval "echo $LEXPATH | sed 's|\(.*\)$LEX$|\1../include|'"`])
 
 AC_CHECK_PROG([YACC], [bison], [bison])
 if test "x$YACC" = "x"; then