WCF Certificate Authentication Problems

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Hi,
I am trying to configure my service to authenticate clients using
certificates.
Here is the relevant portion of the web.config:
<system.serviceModel>
<services>
<service behaviorConfiguration="returnFaults" name="WCFSecureService">
<endpoint binding="wsHttpBinding"
bindingConfiguration="TransportSecurity"
contract="IWCFSecureService"/>
<endpoint address="mex"
binding="mexHttpsBinding"
name="MetadataBinding"
contract="IMetadataExchange"/>
</service>
</services>

<behaviors>
<serviceBehaviors>
<behavior name="returnFaults">
<serviceDebug includeExceptionDetailInFaults="true"/>
<serviceMetadata httpsGetEnabled="true"/>
<serviceTimeouts/>
</behavior>
</serviceBehaviors>
</behaviors>

<bindings>
<wsHttpBinding>
<binding name="TransportSecurity">
<security mode="Transport">
<transport clientCredentialType="Certificate"/>
</security>
</binding>
</wsHttpBinding>
</bindings>
</system.serviceModel>

When testing this service I am getting the following exception:
The SSL settings for the service 'None' does not match those of the IIS
'Ssl, SslNegotiateCert, SslRequireCert'.
Prior to the exception I am being prompted to select a certificate from the
list.

I am hosting this service in IIS and the virtual directory for this serice
is configured with the following settings:
Require secure channel (IIS is setup with a certificate).
Client Certificate -Require client certificates.

I assume that the issue is somewhere around mismatch between IIS
configuation and Service configuration, but I am unable to find documentation
on how those two should be configured in this scenario.

Thanks in advance.
Alex.