diff --git a/platform/lang-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java b/platform/lang-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java
index ca5790dbb3e1..c4a935a73757 100644
--- a/platform/lang-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java
+++ b/platform/lang-impl/src/com/intellij/psi/impl/source/PsiFileImpl.java
@@ -385,6 +385,9 @@ public abstract class PsiFileImpl extends ElementBase implements PsiFileEx, PsiF
   protected PsiFileImpl clone() {
     FileViewProvider provider = getViewProvider().clone();
     final Language language = getLanguage();
+    if (provider == null) {
+      throw new AssertionError("Unable to clone the view provider: " + getViewProvider() + "; " + language);
+    }
     PsiFileImpl clone = (PsiFileImpl)provider.getPsi(language);
     assert clone != null:"Cannot find psi file with language:"+language + " from viewprovider:"+provider+" virtual file:"+getVirtualFile();