I am trying to write a utility to retrieve API keys and secrets from datastore using Objectify-6.1.0 and make them available as a static entity, Util. This compiles OK, but the ofy().save() in the last line of the static block throws the runtime error below. Please help me understand why this happens and how to fix it. Thanks.

package org.chemvantage;
import static com.googlecode.objectify.ObjectifyService.ofy;
import com.googlecode.objectify.annotation.Entity;
import com.googlecode.objectify.annotation.Id;

@entity
public class Util {
static Util u;
@id static Long id;
private static String HMAC256Secret = "ChangeMe";

static {
	try {  // Load entity from datastore when new software version is deployed
		u = ofy().load().type(Util.class).first().safe();
	} catch (Exception e) {  // Run once when datastore is initiated
		ofy().save().entity(new Util());
	}
}

private Util() {}

protected static String getHMAC256Secret() { 
	return HMAC256Secret; 
}

}

java.lang.invoke.WrongMethodTypeException: cannot convert MethodHandle()Long to (Object)Object
at java.base/java.lang.invoke.MethodHandle.asTypeUncached(MethodHandle.java:903) ~[na:na]
at java.base/java.lang.invoke.MethodHandle.asType(MethodHandle.java:870) ~[na:na]
at java.base/java.lang.invoke.Invokers.checkGenericType(Invokers.java:541) ~[na:na]
at com.googlecode.objectify.impl.FieldProperty.get(FieldProperty.java:89) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.KeyMetadata.getId(KeyMetadata.java:318) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.KeyMetadata.requiresAutogeneratedId(KeyMetadata.java:330) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.Keys.requiresAutogeneratedId(Keys.java:139) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.Deferrer.undefer(Deferrer.java:79) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.WriteEngine.save(WriteEngine.java:68) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.SaverImpl.entities(SaverImpl.java:60) ~[objectify-6.1.0.jar:na]
at com.googlecode.objectify.impl.SaverImpl.entity(SaverImpl.java:35) ~[objectify-6.1.0.jar:na]
at org.chemvantage.Util.(Util.java:18) ~[classes/:na]
at org.chemvantage.HelloWorld.doGet(HelloWorld.java:23) ~[classes/:na]
...