Why is the WCF service not working with the following configuration?

I have a WCF service with the configuration file below. Although I indicated clientCredentialType = Nonethe WCF service (from VS2013) throws an exception, indicating that the certificate is not specified.

Why is that? If a certificate is not required, only if clientCredentialTypeinstalled as a certificate.

<system.serviceModel>
    <bindings>
      <wsHttpBinding>
        <binding>
          <security mode="Message">
            <message clientCredentialType="Windows"/>
          </security>
        </binding>
      </wsHttpBinding>
    </bindings>
    <services>
      <service name="WCFBindingwshttpBinding.Service1">
        <endpoint address="" binding="wsHttpBinding" bindingConfiguration="" contract="WCFBindingwshttpBinding.IService1">
          <identity>
            <dns value="localhost" />
          </identity>
        </endpoint>
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8733/Design_Time_Addresses/WCFBindingwshttpBinding/Service1/" />
          </baseAddresses>
        </host>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <!-- To avoid disclosing metadata information, 
          set the values below to false before deployment -->
          <serviceMetadata httpGetEnabled="True" httpsGetEnabled="True"/>
          <!-- To receive exception details in faults for debugging purposes, 
          set the value below to true.  Set to false before deployment 
          to avoid disclosing exception information -->
          <serviceDebug includeExceptionDetailInFaults="False" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>