diff --git a/xml/dom-impl/src/com/intellij/util/xml/impl/DomImplUtil.java b/xml/dom-impl/src/com/intellij/util/xml/impl/DomImplUtil.java
index d661a720598c..93befc41fac6 100644
--- a/xml/dom-impl/src/com/intellij/util/xml/impl/DomImplUtil.java
+++ b/xml/dom-impl/src/com/intellij/util/xml/impl/DomImplUtil.java
@@ -144,7 +144,12 @@ public class DomImplUtil {
   }
 
   public static List<XmlTag> findSubTags(@NotNull XmlTag tag, final EvaluatedXmlName name, final XmlFile file) {
-    return findSubTags(tag.getSubTags(), name, file);
+    assert tag.isValid();
+    XmlTag[] subTags = tag.getSubTags();
+    for (XmlTag subTag : subTags) {
+      assert subTag.isValid() : "tag.getSubTags() returned invalid, tag=" + tag + ", subTag.parent=" + subTag.getNode().getTreeParent();
+    }
+    return findSubTags(subTags, name, file);
   }
 
   public static List<XmlTag> findSubTags(final XmlTag[] tags, final EvaluatedXmlName name, final XmlFile file) {