diff --git a/src/Generator/MoGenerator.php b/src/Generator/MoGenerator.php
index 55815822..5edb68e0 100644
--- a/src/Generator/MoGenerator.php
+++ b/src/Generator/MoGenerator.php
@@ -67,7 +67,7 @@ public function generateString(Translations $translations): string
 
             $originalsIndex[] = [
                 'relativeOffset' => strlen($originalsTable),
-                'length' => strlen($originalString),
+                'length' => strlen((string) $originalString),
             ];
             $originalsTable .= $originalString."\x00";
             $translationsIndex[] = [
diff --git a/tests/MoGeneratorTest.php b/tests/MoGeneratorTest.php
index 2e1eff62..06b3f5d9 100644
--- a/tests/MoGeneratorTest.php
+++ b/tests/MoGeneratorTest.php
@@ -23,7 +23,7 @@ public function testMoGenerator()
             ->set('X-Generator', 'PHP-Gettext');
 
         $translation = Translation::create('context-1', 'Original');
-        $translation->translate('Orixintal');
+        $translation->translate('Orixinal');
         $translations->add($translation);
 
         $translation = Translation::create('context-1', 'Other comment', 'Other comments');
@@ -36,6 +36,10 @@ public function testMoGenerator()
         $translation->translate('Comentario deshabilitado');
         $translations->add($translation);
 
+        $translation = Translation::create(null, '123456');
+        $translation->translate('12345');
+        $translations->add($translation);
+
         $mo = $generator->generateString($translations);
         $expected = file_get_contents(__DIR__.'/assets/mo-generator-result.mo');
 
@@ -43,7 +47,7 @@ public function testMoGenerator()
 
         $result = $loader->loadString($mo);
 
-        $this->assertCount(2, $result);
+        $this->assertCount(3, $result);
         $this->assertCount(5, $result->getHeaders());
     }
 }
diff --git a/tests/assets/mo-generator-result.mo b/tests/assets/mo-generator-result.mo
index f055a073..cc7feb7c 100644
Binary files a/tests/assets/mo-generator-result.mo and b/tests/assets/mo-generator-result.mo differ