diff --git a/lib/ildus/server/account_backends/yaml.rb b/lib/ildus/server/account_backends/yaml.rb
index 5bf3b91..8f24945 100644
--- a/lib/ildus/server/account_backends/yaml.rb
+++ b/lib/ildus/server/account_backends/yaml.rb
@@ -22,6 +22,7 @@ module Ildus::Server::AccountBackend
       case config['crypt'].to_sym
         when :unix
           regged_pass = @db[user]
+          return false if regged_pass.nil?
           self.auth = (pass.crypt(regged_pass) == regged_pass)
         else
           raise "unsupported crypt type: #{config['crypt']}"
diff --git a/lib/ildus/server/domain_backends/ldap.rb b/lib/ildus/server/domain_backends/ldap.rb
index 5f61e48..5332137 100644
--- a/lib/ildus/server/domain_backends/ldap.rb
+++ b/lib/ildus/server/domain_backends/ldap.rb
@@ -67,10 +67,12 @@ module Ildus::Server::DomainBackend
       raise Handler::HostNotFoundError if entry.nil?
 
       if addr.ipv4?
-        return false if entry['aRecord'][0] == addr.to_s
+        record = entry['aRecord']
+        return false if record and record[0] == addr.to_s
         @ldap.modify(entry['dn'][0], {"aRecord"    => [addr.to_s]})
       elsif addr.ipv6?
-        return false if entry['aAAARecord'][0] == addr.to_s
+        record = entry['aAAARecord']
+        return false if record and record[0] == addr.to_s
         @ldap.modify(entry['dn'][0], {"aAAARecord" => [addr.to_s]})
       else
         return false