erro (admin.E108)

Quando vou executar o makemigrations aparece este erro: <class 'escola.admin.Matriculas'>: (admin.E108) The value of 'list_display[1]' refers to 'aluno', which is not a callable, an attribute of 'Matriculas', or an attribute or method on 'escola.Matricula'.

Meu arquivo models.py:

from django.db import models

class Alunos(models.Model):
    nome = models.CharField(max_length=30)
    rg = models.CharField(max_length=9)
    cpf = models.CharField(max_length=11)
    data_nascimento = models.DateField()

    def __str__(self):
        return self.nome


class Curso(models.Model):
    NIVEL = (
        ('B', 'Básico'),
        ('I', 'Intermediário'),
        ('A', 'Avançado')
    )

    codigo_curso = models.CharField(max_length=10)
    descricao = models.CharField(max_length=100)
    nivel = models.CharField(max_length=1, choices=NIVEL, blank=False, null=False, default='B')

    def __str__(self):
        return self.descricao


class Matricula(models.Model):
    PERIODO = (
        ('M', 'Matutino'),
        ('V', 'Vespertino'),
        ('N', 'Noturno')
    )
    nome = models.ForeignKey(Alunos, on_delete=models.CASCADE)
    curso = models.ForeignKey(Curso, on_delete=models.CASCADE)
    periodo = models.CharField(max_length=1, choices=PERIODO, blank=False, null=False, default='M')

Meu arquivo admin.py:

from django.contrib import admin
from escola.models import Alunos, Curso, Matricula

class AlunosAdmin(admin.ModelAdmin):
    list_display = ('id', 'nome', 'rg', 'cpf', 'data_nascimento')
    list_display_links = ('id', 'nome')
    search_fields = ('nome', )
    list_per_page = 20


admin.site.register(Alunos, AlunosAdmin)


class Cursos(admin.ModelAdmin):
    list_display = ('id', 'codigo_curso', 'descricao')
    list_display_links = ('id', 'codigo_curso')
    search_fields = ('codigo_curso', )

admin.site.register(Curso, Cursos)


class Matriculas(admin.ModelAdmin):
    list_display = ('id', 'aluno', 'curso', 'periodo')
    list_display_links = ('id', )

admin.site.register(Matricula, Matriculas)