diff --git a/library/Opus/Model/Field.php b/library/Opus/Model/Field.php
index 49d7e702..96f2cd59 100644
--- a/library/Opus/Model/Field.php
+++ b/library/Opus/Model/Field.php
@@ -965,10 +965,7 @@ public function setType($type)
         $this->type = $type;
     }
 
-    /**
-     * @return string|null
-     */
-    public function getType()
+    public function getType(): string|null
     {
         return $this->type;
     }
diff --git a/library/Opus/Model/Xml/AbstractVersion.php b/library/Opus/Model/Xml/AbstractVersion.php
index b928f231..1c49afa5 100644
--- a/library/Opus/Model/Xml/AbstractVersion.php
+++ b/library/Opus/Model/Xml/AbstractVersion.php
@@ -394,6 +394,9 @@ public function getFieldValues($field)
         if ($fieldValues instanceof DateTimeZone) {
             $fieldValues = $fieldValues->getName();
         }
+        if ($field->getType() === 'bool') {
+            $fieldValues = $fieldValues ? '1' : '0';
+        }
 
         return trim($fieldValues ?? '');
     }
diff --git a/tests/Opus/Model/Xml/Version1Test.php b/tests/Opus/Model/Xml/Version1Test.php
index 493026b9..6cafc3a8 100644
--- a/tests/Opus/Model/Xml/Version1Test.php
+++ b/tests/Opus/Model/Xml/Version1Test.php
@@ -949,8 +949,6 @@ public function testDateXml()
         $xml->setModel($document);
         $dom = $xml->getDomDocument();
 
-        $output = $dom->saveXml();
-
         $elements = $dom->getElementsByTagName('CompletedDate');
         $this->assertCount(1, $elements);
 
@@ -971,4 +969,18 @@ public function testDateXml()
         $this->assertTrue($completedDate->hasAttribute('Timezone'));
         $this->assertTrue($completedDate->hasAttribute('UnixTimestamp'));
     }
+
+    public function testOutputBelongsToBibliographyFalseAsZero()
+    {
+        $doc = Document::new();
+        $doc->setBelongsToBibliography(false);
+
+        $xml = new Xml();
+        $xml->setStrategy(new Version1());
+        $xml->setModel($doc);
+        $dom = $xml->getDomDocument();
+
+        $docElement = $dom->getElementsByTagName('Opus_Document')->item(0);
+        $this->assertEquals('0', $docElement->attributes->getNamedItem('BelongsToBibliography')->nodeValue);
+    }
 }