diff --git a/src/xapi-object-to-xo.js b/src/xapi-object-to-xo.js
index 42a54f318..d218e57c6 100644
--- a/src/xapi-object-to-xo.js
+++ b/src/xapi-object-to-xo.js
@@ -393,7 +393,7 @@ const TRANSFORMS = {
     return {
       type: 'PBD',
 
-      attached: obj.currently_attached,
+      attached: Boolean(obj.currently_attached),
       host: link(obj, 'host'),
       SR: link(obj, 'SR')
     }