diff --git a/src/utils/serialize.js b/src/utils/serialize.js
index 7348608..e066b7f 100644
--- a/src/utils/serialize.js
+++ b/src/utils/serialize.js
@@ -6,8 +6,17 @@ function serializeNode (node, key, data) {
       data.relationships = {}
     }
 
+    const serializeEntity = (entity) => (
+      entity.id
+        ? { id: entity.id, type: entity.type || key }
+        : ( Object.keys(entity).length
+           ? entity // object without ID or type will surely not pass validation
+           : null // encode as null to signal relationship removal
+         )
+    )
+
     data.relationships[key] = {
-      data: node.id ? { id: node.id, type: node.type || key } : node,
+      data: Array.isArray(node) ? node.map(serializeEntity) : serializeEntity(node),
       links: node.links,
       meta: node.meta
     }
@@ -51,4 +60,4 @@ export function serialize (type, data, options = {
   } catch (error) {
     errorParser(error)
   }
-}
\ No newline at end of file
+}