diff --git a/tests/queries/models.py b/tests/queries/models.py
index 523b58c..714ca3f 100644
--- a/tests/queries/models.py
+++ b/tests/queries/models.py
@@ -264,6 +264,14 @@ class Related(models.Model):
     custom = models.ForeignKey(CustomPk, models.CASCADE)
 
 
+class RelatedNull(models.Model):
+    custom = models.ForeignKey(CustomPk, models.CASCADE, null=True)
+    name = models.CharField(max_length=20)
+
+    def __str__(self):
+        return self.name
+
+
 class CustomPkTag(models.Model):
     id = models.CharField(max_length=20, primary_key=True)
     custom_pk = models.ManyToManyField(CustomPk)
diff --git a/tests/queries/tests.py b/tests/queries/tests.py
index e40ab1f..9b13969 100644
--- a/tests/queries/tests.py
+++ b/tests/queries/tests.py
@@ -26,7 +26,7 @@ from .models import (
     Member, ModelA, ModelB, ModelC, ModelD, MyObject, NamedCategory, Node,
     Note, NullableName, Number, ObjectA, ObjectB, ObjectC, OneToOneCategory,
     Order, OrderItem, Page, Paragraph, Person, Plaything, PointerA, Program,
-    ProxyCategory, ProxyObjectA, ProxyObjectB, Ranking, Related,
+    ProxyCategory, ProxyObjectA, ProxyObjectB, Ranking, Related, RelatedNull,
     RelatedIndividual, RelatedObject, Report, ReservedName, Responsibility,
     School, SharedConnection, SimpleCategory, SingleObject, SpecialCategory,
     Staff, StaffUser, Student, Tag, Task, Ticket21203Child, Ticket21203Parent,
@@ -3813,3 +3813,17 @@ class Ticket23622Tests(TestCase):
             Ticket23605A.objects.filter(qx),
             [a2], lambda x: x
         )
+
+class Ticket26983Tests(TestCase):
+    def test_ticket_26983(self):
+        custom = CustomPk.objects.create(name="pk")
+        RelatedNull.objects.create(name="null")
+        RelatedNull.objects.create(name="not null", custom=custom)
+        self.assertQuerysetEqual(
+            RelatedNull.objects.filter(custom__isnull=False),
+            ['<RelatedNull: not null>']
+        )
+        self.assertQuerysetEqual(
+            RelatedNull.objects.filter(custom__isnull=True),
+            ['<RelatedNull: null>']
+        )