Returning SimpleStruct with default_value attribute from abstract method results in C-side compiler error

Here's an example of such code:

[CCode (default_value = "{.member = 5}")]
[SimpleType]
public struct SimpleStruct {
	uint8 member;
}

public abstract interface ExampleIface {
	public abstract SimpleStruct my_method();
}

And this is troublesome method this generates in C code (#line directives omitted, comments added by me):

SimpleStruct
example_iface_my_method (ExampleIface* self)
{
	ExampleIfaceIface* _iface_;
	g_return_val_if_fail (self != NULL, {.member = 5}); //< First error here
	_iface_ = EXAMPLE_IFACE_GET_INTERFACE (self);
	if (_iface_->my_method) {
		return _iface_->my_method (self);
	}
	return {.member = 5}; //< Second error here
}

From my understanding, this can be solved by explicitly casting default_value expression to relevant structure type, either always (to prevent potential issues like those from cropping up ever again) or only in those specific cases.