Forgot to maintain the toString() proper.
diff --git a/core/runtime/src/main/java/org/apache/polygene/runtime/value/ValueInstance.java b/core/runtime/src/main/java/org/apache/polygene/runtime/value/ValueInstance.java
index 8af2e08..79deff9 100644
--- a/core/runtime/src/main/java/org/apache/polygene/runtime/value/ValueInstance.java
+++ b/core/runtime/src/main/java/org/apache/polygene/runtime/value/ValueInstance.java
@@ -158,6 +158,11 @@
     @Override
     public String toString()
     {
+        String json = toJsonString();
+        if( json != null )
+        {
+            return json;
+        }
         return "ValueInstance{" +
                "mixins=" + Arrays.toString( mixins ) +
                ", state=" + state +