diff --git a/core/src/PlainFactory.ts b/core/src/PlainFactory.ts
index 410c23d..bd0b6d3 100644
--- a/core/src/PlainFactory.ts
+++ b/core/src/PlainFactory.ts
@@ -151,7 +151,7 @@ export class PlainFactory implements DataFactory {
   }
 
   public defaultGraph(): NamedNode {
-    return this.namedNode("")
+    return this.namedNode("rdf:defaultGraph")
   }
 
   /**