[keycloak-user] Getting 'Failed to find provider' when attempting to set default SPI provider

I'm trying to use a custom Email sender provider with keycloak 3.4.3.Final but something isn't working correctly because keycloak fails to start up with: java.lang.RuntimeException: Failed to find provider serviceEmailSender for emailSender I'm deploying the provider via a war in the /deployments directory. I have the factory class listed in the META-INF/services/org.keycloak.email.EmailSenderProviderFactory file I've added this to the keycloak-server subsystem <spi name="emailSender"> <default-provider>serviceEmailSender</default-provider> <provider name="serviceEmailSender" enabled="true"/> </spi> If I leave out the <default-provider> entry and restart the server I can see that the init() method is called on my EmailSenderProviderFactory implementation so as far as I can tell everything is configured correctly. But keycloak doesn't like when I try to set this provider as the default. Is there something I'm missing? Jared