diff --git a/bundles/org.eclipse.vorto.perspective.vorto/src/org/eclipse/vorto/perspective/vorto/dnd/dropvalidation/DatatypeValidator.java b/bundles/org.eclipse.vorto.perspective.vorto/src/org/eclipse/vorto/perspective/vorto/dnd/dropvalidation/DatatypeValidator.java
index 06d5ee3136..b3b31ec48f 100644
--- a/bundles/org.eclipse.vorto.perspective.vorto/src/org/eclipse/vorto/perspective/vorto/dnd/dropvalidation/DatatypeValidator.java
+++ b/bundles/org.eclipse.vorto.perspective.vorto/src/org/eclipse/vorto/perspective/vorto/dnd/dropvalidation/DatatypeValidator.java
@@ -17,6 +17,7 @@
 import org.eclipse.vorto.core.api.model.datatype.Entity;
 import org.eclipse.vorto.core.api.model.datatype.Enum;
 import org.eclipse.vorto.core.api.model.model.Model;
+import org.eclipse.vorto.core.ui.MessageDisplayFactory;
 import org.eclipse.vorto.core.ui.model.IModelElement;
 import org.eclipse.vorto.perspective.dnd.dropvalidator.TargetClassSourceClassValidator;
 
@@ -30,8 +31,10 @@ public DatatypeValidator(Class<?> targetClass, Class<?> sourceClass) {
 	public boolean allow(Object receivingModelElement, Object droppedObject) {
 		if (receivingModelElement instanceof IModelElement && droppedObject instanceof IModelElement) {
 			boolean entityDroppedToEnum = entityDroppedToEnum(((IModelElement)receivingModelElement).getModel(), ((IModelElement) droppedObject).getModel());
-			return super.allow(receivingModelElement, droppedObject) && !entityDroppedToEnum;
+			boolean enumDroppedToEnum = enumDroppedToEnum(((IModelElement)receivingModelElement).getModel(), ((IModelElement) droppedObject).getModel());
+			return super.allow(receivingModelElement, droppedObject) && !entityDroppedToEnum && !enumDroppedToEnum;
 		} else {
+			MessageDisplayFactory.getMessageDisplay().displayError("You cannot drop an Entity or Enum into an Enum");
 			return false;
 		}
 	}
@@ -39,4 +42,8 @@ public boolean allow(Object receivingModelElement, Object droppedObject) {
 	private boolean entityDroppedToEnum(Model targetModel, Model droppedModel) {
 		return targetModel instanceof Enum && droppedModel instanceof Entity;
 	}
+	
+	private boolean enumDroppedToEnum(Model targetModel, Model droppedModel) {
+		return targetModel instanceof Enum && droppedModel instanceof Enum;
+	}
 }
diff --git a/framework/org.eclipse.vorto.perspective/src/org/eclipse/vorto/perspective/dnd/dropvalidator/TargetClassModelTypeValidator.java b/framework/org.eclipse.vorto.perspective/src/org/eclipse/vorto/perspective/dnd/dropvalidator/TargetClassModelTypeValidator.java
index eedb7882a2..7d50ab9700 100644
--- a/framework/org.eclipse.vorto.perspective/src/org/eclipse/vorto/perspective/dnd/dropvalidator/TargetClassModelTypeValidator.java
+++ b/framework/org.eclipse.vorto.perspective/src/org/eclipse/vorto/perspective/dnd/dropvalidator/TargetClassModelTypeValidator.java
@@ -39,7 +39,7 @@ public boolean allow(Object receivingModelElement, Object droppedObject) {
 			ModelResource model = (ModelResource) droppedObject;
 			return model.getId().getModelType() == modelType;
 		} else {
-			if (!targetClass.isInstance(receivingModelElement)) {
+			if (droppedObject instanceof ModelResource && !targetClass.isInstance(receivingModelElement)) {
 				MessageDisplayFactory.getMessageDisplay().displayError("Please create a Project first before dropping models from the repository.");
 			}
 			return false;