diff --git a/crud/src/main/java/com/redhat/lightblue/eval/SetExpressionEvaluator.java b/crud/src/main/java/com/redhat/lightblue/eval/SetExpressionEvaluator.java
index d398f2ee..fd72f570 100644
--- a/crud/src/main/java/com/redhat/lightblue/eval/SetExpressionEvaluator.java
+++ b/crud/src/main/java/com/redhat/lightblue/eval/SetExpressionEvaluator.java
@@ -26,14 +26,15 @@
 import org.slf4j.LoggerFactory;
 
 import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.JsonNodeFactory;
 import com.fasterxml.jackson.databind.node.ObjectNode;
-import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.redhat.lightblue.crud.CrudConstants;
 import com.redhat.lightblue.metadata.ArrayField;
 import com.redhat.lightblue.metadata.FieldTreeNode;
 import com.redhat.lightblue.metadata.ObjectArrayElement;
 import com.redhat.lightblue.metadata.ObjectField;
+import com.redhat.lightblue.metadata.ReferenceField;
 import com.redhat.lightblue.metadata.SimpleArrayElement;
 import com.redhat.lightblue.metadata.SimpleField;
 import com.redhat.lightblue.metadata.Type;
@@ -134,14 +135,23 @@ public SetExpressionEvaluator(JsonNodeFactory factory, FieldTreeNode context, Se
 
             if (mdNode instanceof SimpleField || mdNode instanceof SimpleArrayElement) {
                 data = initializeSimple(rvalue, refMdNode, mdNode, field, refPath);
+                setValues.add(data);
+            } else if (mdNode instanceof ReferenceField) {
+                if (rvalue.getValue() != null) {
+                    throw new EvaluationError(CrudConstants.ERR_ASSIGNMENT + field +" can't assign values to referenced fields");
+                } else {
+                    // ignore if null
+                }
             } else if (mdNode instanceof ObjectField || mdNode instanceof ObjectArrayElement) {
                 data = initializeObject(rvalue, refMdNode, mdNode, field, refPath);
+                setValues.add(data);
             } else if (mdNode instanceof ArrayField) {
                 data = initializeArray(rvalue, refMdNode, mdNode, field, refPath);
-            }
-            if (data != null) {
                 setValues.add(data);
+            } else {
+                throw new EvaluationError(CrudConstants.ERR_ASSIGNMENT + field + " field type "+mdNode.getClass()+" is not recognized!");
             }
+
         }
     }
 
diff --git a/crud/src/test/java/com/redhat/lightblue/eval/SetExpressionEvaluatorTest.java b/crud/src/test/java/com/redhat/lightblue/eval/SetExpressionEvaluatorTest.java
index 3cd5e099..d1cb88cb 100644
--- a/crud/src/test/java/com/redhat/lightblue/eval/SetExpressionEvaluatorTest.java
+++ b/crud/src/test/java/com/redhat/lightblue/eval/SetExpressionEvaluatorTest.java
@@ -100,4 +100,20 @@ public void assign_arr_to_field() throws Exception {
         Assert.assertEquals("[1,2]", jsonDoc.get(new Path("field6.nf10")).toString());
 
     }
+
+    @Test
+    public void setting_reference_to_null_is_ignored() throws Exception {
+        UpdateExpression expr = EvalTestContext.updateExpressionFromJson("{'$set': {'ref': null } }");
+        Updater updater = Updater.getInstance(JSON_NODE_FACTORY, md, expr);
+        Assert.assertFalse(updater.update(jsonDoc, md.getFieldTreeRoot(), new Path()));
+
+    }
+
+    @Test(expected=EvaluationError.class)
+    public void setting_reference_to_non_null_throws_exception() throws Exception {
+        UpdateExpression expr = EvalTestContext.updateExpressionFromJson("{'$set': {'ref': 'foo' } }");
+        Updater updater = Updater.getInstance(JSON_NODE_FACTORY, md, expr);
+        Assert.assertFalse(updater.update(jsonDoc, md.getFieldTreeRoot(), new Path()));
+
+    }
 }
diff --git a/crud/src/test/resources/testMetadata.json b/crud/src/test/resources/testMetadata.json
index 95b45365..d626a5e7 100644
--- a/crud/src/test/resources/testMetadata.json
+++ b/crud/src/test/resources/testMetadata.json
@@ -270,6 +270,11 @@
                   }
               }
           }
+      },
+	  "ref" : {
+          "type":"reference",
+          "entity":"referenced_entity",
+          "query": { "field":"field1","op":"=","rfield":"$parent.field1"}
       }
     }
   }