--- a/configure.in.orig	2015-06-16 20:40:02.938216001 +0800
+++ b/configure.in	2015-06-16 20:40:16.198216001 +0800
@@ -399,7 +399,7 @@ AS_IF([test "x$ac_cv_header_xcrypt_h" =
   [crypt_libs="crypt"])
 
 BACKUP_LIBS=$LIBS
-AC_SEARCH_LIBS([crypt],[$crypt_libs], LIBCRYPT="-l$ac_lib", LIBCRYPT="")
+AC_SEARCH_LIBS([crypt],[$crypt_libs], LIBCRYPT="${ac_lib:+-l$ac_lib}", LIBCRYPT="")
 AC_CHECK_FUNCS(crypt_r crypt_gensalt_r)
 LIBS=$BACKUP_LIBS
 AC_SUBST(LIBCRYPT)