What makes the FederatedAuthentication.SessionAuthenticationModule return NULL?

I'm not sure why but my FederatedAuthentication.SessionAuthenticationModule is resolving as NULL and crashing my app when I try to run my ClaimsTransformer() module:

    public void EstablishSession(ClaimsPrincipal principal)
    {
        var sessionToken = new SessionSecurityToken(principal, TimeSpan.FromHours(8))
        {
            IsPersistent = false, // make persistent
            IsReferenceMode = true // cache on server
        };


        FederatedAuthentication.SessionAuthenticationModule.WriteSessionTokenToCookie(sessionToken);
       // FederatedAuthentication.SessionAuthenticationModule == null and I throw an error :(
    }

Here's what's in my web.config:

<configSections>
  <section name="system.identityModel" type="System.IdentityModel.Configuration.SystemIdentityModelSection, System.IdentityModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
  <section name="system.identityModel.services" type="System.IdentityModel.Services.Configuration.SystemIdentityModelServicesSection, System.IdentityModel.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
</configSections>
<system.web>
  <authentication mode="None" />
</system.web>
<system.webServer>
  <modules runAllManagedModulesForAllRequests="true">
    <remove name="RoleManager" />
    <remove name="FormsAuthentication" />
    <remove name="SessionAuthenticationModule" />
    <add name="SessionAuthenticationModule" type="System.IdentityModel.Services.SessionAuthenticationModule, System.IdentityModel.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
  </modules>
</system.webServer>
<system.identityModel>
  <identityConfiguration>
    <claimsAuthenticationManager type="Web.Infrastructure.Authentication.ClaimsTransformer, Web" />
  </identityConfiguration>
<