diff --git a/src/Resolver/DeviceResolver.php b/src/Resolver/DeviceResolver.php
index 8fbb546..6a796d7 100644
--- a/src/Resolver/DeviceResolver.php
+++ b/src/Resolver/DeviceResolver.php
@@ -75,6 +75,8 @@ public function resolve(array $data)
             ->setAllowedTypes('lat', 'double')
             ->setDefined('country')
             ->setAllowedTypes('country', 'string')
+            ->setDefined('external_user_id')
+            ->setAllowedTypes('external_user_id', 'string')
             ->setDefault('app_id', $this->config->getApplicationId())
             ->setAllowedTypes('app_id', 'string');
 
diff --git a/tests/OneSignal/Tests/Resolver/DeviceResolverTest.php b/tests/OneSignal/Tests/Resolver/DeviceResolverTest.php
index c9633c7..5c99f99 100644
--- a/tests/OneSignal/Tests/Resolver/DeviceResolverTest.php
+++ b/tests/OneSignal/Tests/Resolver/DeviceResolverTest.php
@@ -44,6 +44,7 @@ public function testResolveWithValidValues()
             'long' => 55.1684595,
             'lat' => 22.7624291,
             'country' => 'LT',
+            'external_user_id' => 'value',
             'app_id' => 'value',
         ];
 
@@ -109,6 +110,7 @@ public function wrongValueTypesProvider()
             [['country' => false]],
             [['app_id' => 666]],
             [['device_type' => 666]],
+            [['external_user_id' => 666]],
         ];
     }