EF Code First Multiplicity - entity-framework

Question

I've got the following :
public class ApplicationUser : IdentityUser
{
public ApplicationUser()
{
}
public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
{
// Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
// Add custom user claims here
return userIdentity;
}
[ForeignKey("UserProfile")]
public int UserProfileID { get; set; }
public UserProfile UserProfile { get; set; }
}
}
public class UserProfile : BaseModel
{
[Key]
public int UserProfileID { get; set; }
[Required]
public String FirstName { get; set; }
[Required]
public String LastName { get; set; }
public String LicenseNumber { get; set; }
public String Position { get; set; }
public bool? Active { get; set; }
[Required]
[ForeignKey("ApplicationUser")]
public String AppUserID { get; set; }
public ApplicationUser ApplicationUser { get; set; }
[ForeignKey("Division")]
public int? DivisionID { get; set; }
public virtual Division Division { get; set; }
public virtual ICollection<Building> Buildings { get; set; }
public virtual ICollection<UserProcess> UserProcesses { get; set; }
public UserProfile()
{
Buildings = new HashSet<Building>();
}
}
I'm getting the error
'UserProfile_ApplicationUser_Target: : Multiplicity is not valid in
Role 'UserProfile_ApplicationUser_Target' in relationship
'UserProfile_ApplicationUser'. Because the Dependent Role properties
are not the key properties, the upper bound of the multiplicity of the
Dependent Role must be '*'."
I don't see what's wrong. This should be a 1:1 relationship. An ApplicationUser has a userProfile and UserProfile always has an applicationuser. Is the way I have it coded making it a 1 to many relationship since multiple user profiles could have an ApplicationUser? I want to maintain the int key on UserProfile.