Accessing relationships with strict mode enabled

Hi everyone,

I enabled the strict mode for all models. I have users and workspaces. A user can only have one active workspace.

The relationship on the user looks like this:

public function activeWorkspace(): BelongsTo
{
    return $this->belongsTo(Workspace::class, 'active_workspace_id');
}

Now when trying to set a workspace as active on the user like so: $user->activeWorkspace()->associate($workspace);

...I get this error: The attribute [active_workspace_id] either does not exist or was not retrieved for model [App\Models\User].

I just cannot figure out why this happens. It does not when disabling strict mode.

Does anyone have any idea?

Thanks in advanvce!