diff --git a/src/AddressFormat/AddressFormat.php b/src/AddressFormat/AddressFormat.php
index 88348bbc..5c3a0b0c 100644
--- a/src/AddressFormat/AddressFormat.php
+++ b/src/AddressFormat/AddressFormat.php
@@ -29,6 +29,8 @@ class AddressFormat
      */
     protected array $uppercaseFields = [];
 
+    protected array $defaultValues = [];
+
     protected ?string $administrativeAreaType = null;
 
     protected ?string $localityType = null;
@@ -65,6 +67,10 @@ public function __construct(array $definition)
             AddressField::assertAllExist($definition['required_fields']);
             $this->requiredFields = $definition['required_fields'];
         }
+        if (isset($definition['default_values'])) {
+            AddressField::assertAllExist(array_keys($definition['default_values']));
+            $this->defaultValues = $definition['default_values'];
+        }
         if (isset($definition['uppercase_fields'])) {
             AddressField::assertAllExist($definition['uppercase_fields']);
             $this->uppercaseFields = $definition['uppercase_fields'];
@@ -211,12 +217,24 @@ public function getRequiredFields(): array
 
     /**
      * Gets the list of fields that need to be uppercased.
+     *
+     * @return AddressField[]
      */
     public function getUppercaseFields(): array
     {
         return $this->uppercaseFields;
     }
 
+    /**
+     * Gets the default values.
+     *
+     * @return array The default values, keyed by field name.
+     */
+    public function getDefaultValues(): array
+    {
+        return $this->defaultValues;
+    }
+
     /**
      * Gets the administrative area type.
      *
diff --git a/tests/AddressFormat/AddressFormatTest.php b/tests/AddressFormat/AddressFormatTest.php
index 2afece7a..930188e3 100644
--- a/tests/AddressFormat/AddressFormatTest.php
+++ b/tests/AddressFormat/AddressFormatTest.php
@@ -17,12 +17,11 @@ final class AddressFormatTest extends TestCase
 {
     /**
      * @covers ::__construct
-     *
-     *
      */
-    public function testMissingProperty(): void
+    public function testMissingFormat(): void
     {
         $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Missing required property format.');
         $definition = [
             'country_code' => 'US',
         ];
@@ -31,12 +30,26 @@ public function testMissingProperty(): void
 
     /**
      * @covers ::__construct
-     *
-     *
      */
-    public function testInvalidSubdivision(): void
+    public function testInvalidDefaultValue(): void
     {
         $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('"unknown" is not a valid AddressField value.');
+        $definition = [
+            'country_code' => 'US',
+            'format' => "%givenName %familyName\n%organization\n%addressLine1\n%addressLine2\n%addressLine3\n%dependentLocality",
+            'default_values' => ['unknown' => 'CA'],
+        ];
+        $addressFormat = new AddressFormat($definition);
+    }
+
+    /**
+     * @covers ::__construct
+     */
+    public function testInvalidDependentLocalityType(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('"WRONG" is not a valid DependentLocalityType value.');
         $definition = [
             'country_code' => 'US',
             'format' => "%givenName %familyName\n%organization\n%addressLine1\n%addressLine2\n%addressLine3\n%dependentLocality",
@@ -56,6 +69,7 @@ public function testInvalidSubdivision(): void
      * @covers ::getUsedSubdivisionFields
      * @covers ::getRequiredFields
      * @covers ::getUppercaseFields
+     * @covers ::getDefaultValues
      * @covers ::getAdministrativeAreaType
      * @covers ::getLocalityType
      * @covers ::getDependentLocalityType
@@ -82,6 +96,9 @@ public function testValid(): void
                 AddressField::ADMINISTRATIVE_AREA,
                 AddressField::LOCALITY,
             ],
+            'default_values' => [
+                AddressField::ADMINISTRATIVE_AREA => 'CA',
+            ],
             'administrative_area_type' => AdministrativeAreaType::STATE,
             'locality_type' => LocalityType::CITY,
             'dependent_locality_type' => DependentLocalityType::DISTRICT,
@@ -99,6 +116,7 @@ public function testValid(): void
         $this->assertEquals($definition['local_format'], $addressFormat->getLocalFormat());
         $this->assertEquals($definition['required_fields'], $addressFormat->getRequiredFields());
         $this->assertEquals($definition['uppercase_fields'], $addressFormat->getUppercaseFields());
+        $this->assertEquals($definition['default_values'], $addressFormat->getDefaultValues());
         $this->assertEquals($definition['administrative_area_type'], $addressFormat->getAdministrativeAreaType());
         $this->assertEquals($definition['locality_type'], $addressFormat->getLocalityType());
         // The format has no %dependentLocality, the type must be NULL.