diff --git a/django/db/backends/postgresql/schema.py b/django/db/backends/postgresql/schema.py
index 7687c37fe7..e77915b3b1 100644
--- a/django/db/backends/postgresql/schema.py
+++ b/django/db/backends/postgresql/schema.py
@@ -38,8 +38,11 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     def quote_value(self, value):
         if isinstance(value, str):
             value = value.replace('%', '%%')
+        adapted = psycopg2.extensions.adapt(value)
+        if hasattr(adapted, 'encoding'):
+            adapted.encoding = 'utf8'
         # getquoted() returns a quoted bytestring of the adapted value.
-        return psycopg2.extensions.adapt(value).getquoted().decode()
+        return adapted.getquoted().decode()
 
     def _field_indexes_sql(self, model, field):
         output = super()._field_indexes_sql(model, field)
diff --git a/tests/constraints/models.py b/tests/constraints/models.py
index 1460673a18..f8a4ebe675 100644
--- a/tests/constraints/models.py
+++ b/tests/constraints/models.py
@@ -4,6 +4,7 @@ from django.db import models
 class Product(models.Model):
     price = models.IntegerField(null=True)
     discounted_price = models.IntegerField(null=True)
+    unit = models.CharField(max_length=15, null=True)
 
     class Meta:
         required_db_features = {
@@ -31,6 +32,13 @@ class Product(models.Model):
                 ),
                 name='%(app_label)s_price_neq_500_wrap',
             ),
+            models.CheckConstraint(
+                check=models.Q(
+                    models.Q(unit__isnull=True) |
+                    models.Q(unit__in=['μg/mL', 'ng/mL'])
+                ),
+                name='unicode_unit_list',
+            ),
         ]
 
 
diff --git a/tests/constraints/tests.py b/tests/constraints/tests.py
index d9e91bdf49..2796a0f30b 100644
--- a/tests/constraints/tests.py
+++ b/tests/constraints/tests.py
@@ -88,6 +88,12 @@ class CheckConstraintTests(TestCase):
         with self.assertRaises(IntegrityError):
             Product.objects.create(price=10, discounted_price=20)
 
+    @skipUnlessDBFeature('supports_table_check_constraints')
+    def test_database_constraint_unicode(self):
+        Product.objects.create(price=10, discounted_price=5, unit='μg/mL')
+        with self.assertRaises(IntegrityError):
+            Product.objects.create(price=10, discounted_price=7, unit='l')
+
     @skipUnlessDBFeature('supports_table_check_constraints')
     def test_database_constraint_expression(self):
         Product.objects.create(price=999, discounted_price=5)