diff --git a/jsonld.php b/jsonld.php
index 4238b5f..4391789 100644
--- a/jsonld.php
+++ b/jsonld.php
@@ -1041,8 +1041,16 @@ class JsonLdProcessor {
     }
 
     // graph
-    if($g !== null) {
-      $quad .= " <{$g->nominalValue}>";
+    if($g !== null) {
+      if($g->interfaceName === 'IRI') {
+        $quad .= " <{$g->nominalValue}>";
+      }
+      else if(bnode) {
+        $quad += ' _:g';
+      }
+      else {
+        $quad += " {$g->nominalValue}";
+      }
     }
 
     $quad .= " .\n";