AutoValue classes reject null values, unless the property is annotated with @Nullable. For this reason, the usage of boxed primitives (e.g. Long) is discouraged, except when annotated as @Nullable. Otherwise they can be replaced with the corresponding primitive. There could be some cases where the usage of a boxed primitive might be intentional to avoid boxing the value again after invoking the getter.
Suppress violations by using @SuppressWarnings("AutoValueBoxedValues") on the relevant abstract getter and/or setter.