diff --git a/src/allmydata/test/test_uri.py b/src/allmydata/test/test_uri.py
index d5d260b9e..f6254eb41 100644
--- a/src/allmydata/test/test_uri.py
+++ b/src/allmydata/test/test_uri.py
@@ -470,3 +470,5 @@ class Dirnode(unittest.TestCase):
         self.failIf(IFileURI.providedBy(u1))
         self.failUnless(IDirnodeURI.providedBy(u1))
         self.failUnlessEqual(u1.get_verify_cap(), None)
+        self.failUnlessEqual(u1.get_storage_index(), None)
+        self.failUnlessEqual(u1.abbrev_si(), "<LIT>")
diff --git a/src/allmydata/uri.py b/src/allmydata/uri.py
index c69ed1478..9dd5a5628 100644
--- a/src/allmydata/uri.py
+++ b/src/allmydata/uri.py
@@ -434,7 +434,10 @@ class _DirectoryBaseURI(_BaseURI):
         return self._filenode_uri.to_string().split(':')[2][:5]
 
     def abbrev_si(self):
-        return base32.b2a(self._filenode_uri.get_storage_index())[:5]
+        si = self._filenode_uri.get_storage_index()
+        if si is None:
+            return "<LIT>"
+        return base32.b2a(si)[:5]
 
     def is_mutable(self):
         return True