diff --git a/xml/dom-impl/src/com/intellij/util/xml/impl/DomInvocationHandler.java b/xml/dom-impl/src/com/intellij/util/xml/impl/DomInvocationHandler.java
index d44cc738baee..0f95ee0890a8 100644
--- a/xml/dom-impl/src/com/intellij/util/xml/impl/DomInvocationHandler.java
+++ b/xml/dom-impl/src/com/intellij/util/xml/impl/DomInvocationHandler.java
@@ -161,7 +161,7 @@ public abstract class DomInvocationHandler<T extends AbstractDomChildDescription
 
   public void copyFrom(final DomElement other) {
     if (other == getProxy()) return;
-    assert other.getDomElementType().equals(myType);
+    assert other.getDomElementType().equals(myType) : "Can't copy from " + other.getDomElementType() + " to " + myType;
 
     if (!DomUtil.hasXml(other)) {
       undefine();