diff --git a/src/Kitar/Dynamodb/Model/Model.php b/src/Kitar/Dynamodb/Model/Model.php
index 70afc78..1698f56 100644
--- a/src/Kitar/Dynamodb/Model/Model.php
+++ b/src/Kitar/Dynamodb/Model/Model.php
@@ -74,7 +74,7 @@ public function getKey()
         $missingKeys = [];
 
         foreach ($key as $name => $value) {
-            if (empty($value)) {
+            if (! isset($value) || $value === '') {
                 $missingKeys[] = $name;
             }
         }
diff --git a/tests/Model/ModelTest.php b/tests/Model/ModelTest.php
index 7660bb8..44ddf41 100644
--- a/tests/Model/ModelTest.php
+++ b/tests/Model/ModelTest.php
@@ -162,21 +162,25 @@ public function it_can_create_instance_with_existing_data()
     /** @test */
     public function it_can_process_get_key_with_primary_key()
     {
-        $user = new UserA(['partition' => 'p']);
+        $user1 = new UserA(['partition' => 'p']);
+        $user2 = new UserA(['partition' => "0"]);
+        $user3 = new UserA(['partition' => 0]);
 
-        $this->assertEquals(['partition' => 'p'], $user->getKey());
+        $this->assertEquals(['partition' => 'p'], $user1->getKey());
+        $this->assertEquals(['partition' => "0"], $user2->getKey());
+        $this->assertEquals(['partition' => 0], $user3->getKey());
     }
 
-
     /** @test */
     public function it_can_process_get_key_with_primary_key_and_sort_key()
     {
-        $user = new UserB(['partition' => 'p', 'sort' => 's']);
+        $user1 = new UserB(['partition' => 'p', 'sort' => 's']);
+        $user2 = new UserB(['partition' => 'p', 'sort' => "0"]);
+        $user3 = new UserB(['partition' => 'p', 'sort' => 0]);
 
-        $this->assertEquals([
-            'partition' => 'p',
-            'sort' => 's'
-        ], $user->getKey());
+        $this->assertEquals(['partition' => 'p', 'sort' => 's'], $user1->getKey());
+        $this->assertEquals(['partition' => 'p', 'sort' => "0"], $user2->getKey());
+        $this->assertEquals(['partition' => 'p', 'sort' => 0], $user3->getKey());
     }
 
     /** @test */