Index: lucene/core/src/java/org/apache/lucene/util/fst/FST.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/util/fst/FST.java	(revision 1512816)
+++ lucene/core/src/java/org/apache/lucene/util/fst/FST.java	(working copy)
@@ -1140,7 +1140,6 @@
   /** Finds an arc leaving the incoming arc, replacing the arc in place.
    *  This returns null if the arc was not found, else the incoming arc. */
   public Arc<T> findTargetArc(int labelToMatch, Arc<T> follow, Arc<T> arc, BytesReader in) throws IOException {
-    assert assertRootArcs();
 
     if (labelToMatch == END_LABEL) {
       if (follow.isFinal()) {
@@ -1162,6 +1161,7 @@
 
     // Short-circuit if this arc is in the root arc cache:
     if (follow.target == startNode && labelToMatch < cachedRootArcs.length) {
+      assert assertRootArcs();
       final Arc<T> result = cachedRootArcs[labelToMatch];
       if (result == null) {
         return null;