Index: lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java	(revision 1395515)
+++ lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java	(working copy)
@@ -1488,4 +1488,32 @@
       }
     }
   }
+
+  public void testEmptyFST() throws Exception {
+    final ByteSequenceOutputs outputs = ByteSequenceOutputs.getSingleton();
+    FST<BytesRef> fst = Builder.getEmptyFST(FST.INPUT_TYPE.BYTE1, outputs);
+
+    //System.out.println("SAVE out.dot");
+    //Writer w = new OutputStreamWriter(new FileOutputStream("/x/tmp/out.dot"));
+    //Util.toDot(fst, w, false, false);
+    //w.close();
+
+    for(int i=0;i<2;i++) {
+      assertNull(Util.get(fst, toIntsRef(new BytesRef(), new IntsRef())));
+      assertNull(Util.get(fst, toIntsRef(new BytesRef("foo"), new IntsRef())));
+      BytesRefFSTEnum<BytesRef> fstEnum = new BytesRefFSTEnum<BytesRef>(fst);
+      assertNull(fstEnum.next());
+
+      // Make sure it still works after save/load:
+      Directory dir = newDirectory();
+      IndexOutput out = dir.createOutput("fst", IOContext.DEFAULT);
+      fst.save(out);
+      out.close();
+
+      IndexInput in = dir.openInput("fst", IOContext.DEFAULT);
+      fst = new FST<BytesRef>(in, outputs);
+      in.close();
+      dir.close();
+    }
+  }
 }
Index: lucene/core/src/java/org/apache/lucene/util/fst/BytesRefFSTEnum.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/util/fst/BytesRefFSTEnum.java	(revision 1395515)
+++ lucene/core/src/java/org/apache/lucene/util/fst/BytesRefFSTEnum.java	(working copy)
@@ -25,7 +25,7 @@
 /** Enumerates all input (BytesRef) + output pairs in an
  *  FST.
  *
-  * @lucene.experimental
+ * @lucene.experimental
 */
 
 public final class BytesRefFSTEnum<T> extends FSTEnum<T> {
Index: lucene/core/src/java/org/apache/lucene/util/fst/FSTEnum.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/util/fst/FSTEnum.java	(revision 1395515)
+++ lucene/core/src/java/org/apache/lucene/util/fst/FSTEnum.java	(working copy)
@@ -95,6 +95,10 @@
       //System.out.println("  init");
       upto = 1;
       fst.readFirstTargetArc(getArc(0), getArc(1), fstReader);
+      if (getArc(1).isLast() && !fst.targetHasArcs(getArc(1)) && !getArc(1).isFinal()) {
+        upto = 0;
+        return;
+      }
     } else {
       // pop
       //System.out.println("  check pop curArc target=" + arcs[upto].target + " label=" + arcs[upto].label + " isLast?=" + arcs[upto].isLast());
Index: lucene/core/src/java/org/apache/lucene/util/fst/Builder.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/util/fst/Builder.java	(revision 1395515)
+++ lucene/core/src/java/org/apache/lucene/util/fst/Builder.java	(working copy)
@@ -626,4 +626,16 @@
       }
     }
   }
+
+  /** Returns an FST accepting nothing. */
+  public static <T> FST<T> getEmptyFST(FST.INPUT_TYPE inputType, Outputs<T> outputs) throws IOException {
+    CompiledNode end = new CompiledNode();
+    Builder<T> b = new Builder<T>(inputType, outputs);
+    FST<T> emptyFST = new FST<T>(inputType, outputs, false, 0);
+    end.node = emptyFST.addNode(new UnCompiledNode<T>(b, 1));
+    UnCompiledNode<T> start = new UnCompiledNode<T>(b, 0);
+    start.addArc(0, end);
+    emptyFST.finish(emptyFST.addNode(start));
+    return emptyFST;
+  }
 }