diff --git a/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java b/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java
index 197ab3155f9..b118c13b0a5 100644
--- a/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java
+++ b/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java
@@ -313,10 +313,7 @@ final class DefaultIndexingChain extends DocConsumer {
 
   @Override
   public void abort() {
-    try {
-      storedFieldsConsumer.abort();
-    } catch (Throwable t) {
-    }
+    storedFieldsConsumer.abort();
 
     try {
       // E.g. close any open files in the term vectors writer:
diff --git a/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java b/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
index 7f0b97c6bab..0fc2e2476a8 100644
--- a/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
@@ -1034,17 +1034,17 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable {
 
   /** Confirms that the incoming index sort (if any) matches the existing index sort (if any).
    *  This is unfortunately just best effort, because it could be the old index only has unsorted flushed segments built
-   *  before {@link Version#LUCENE_7_0_0} (flushed segments are sorted in Lucene 7.0).  */
-  private void validateIndexSort() {
+   *  before {@link Version#LUCENE_6_5_0} (flushed segments are sorted in Lucene 7.0).  */
+  private void validateIndexSort() throws CorruptIndexException {
     Sort indexSort = config.getIndexSort();
     if (indexSort != null) {
       for(SegmentCommitInfo info : segmentInfos) {
         Sort segmentIndexSort = info.info.getIndexSort();
         if (segmentIndexSort != null && indexSort.equals(segmentIndexSort) == false) {
           throw new IllegalArgumentException("cannot change previous indexSort=" + segmentIndexSort + " (from segment=" + info + ") to new indexSort=" + indexSort);
-        } else if (segmentIndexSort == null) {
-          // Flushed segments are not sorted if they were built with a version prior to 7.0
-          assert info.info.getVersion().onOrAfter(Version.LUCENE_7_0_0) == false;
+        } else if (segmentIndexSort == null && info.info.getVersion().onOrAfter(Version.LUCENE_6_5_0)) {
+          // Flushed segments are not sorted if they were built with a version prior to 6.5.0
+          throw new CorruptIndexException("segment not sorted with indexSort=" + segmentIndexSort, info.info.toString());
         }
       }
     }
diff --git a/lucene/core/src/java/org/apache/lucene/index/SortingLeafReader.java b/lucene/core/src/java/org/apache/lucene/index/SortingLeafReader.java
index b36b284d780..f24a4d0728e 100644
--- a/lucene/core/src/java/org/apache/lucene/index/SortingLeafReader.java
+++ b/lucene/core/src/java/org/apache/lucene/index/SortingLeafReader.java
@@ -42,7 +42,7 @@ import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
 
 /**
  * An {@link org.apache.lucene.index.LeafReader} which supports sorting documents by a given
- * {@link Sort}. This is package private and is only used by Lucene fo BWC when it needs to merge
+ * {@link Sort}. This is package private and is only used by Lucene for BWC when it needs to merge
  * an unsorted flushed segment built by an older version (newly flushed segments are sorted since version 7.0).
  *
  * @lucene.experimental
diff --git a/lucene/test-framework/src/java/org/apache/lucene/codecs/asserting/AssertingLiveDocsFormat.java b/lucene/test-framework/src/java/org/apache/lucene/codecs/asserting/AssertingLiveDocsFormat.java
index afc80d52642..f4abb54e803 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/codecs/asserting/AssertingLiveDocsFormat.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/codecs/asserting/AssertingLiveDocsFormat.java
@@ -68,13 +68,8 @@ public class AssertingLiveDocsFormat extends LiveDocsFormat {
 
   @Override
   public void writeLiveDocs(MutableBits bits, Directory dir, SegmentCommitInfo info, int newDelCount, IOContext context) throws IOException {
-    MutableBits raw = bits;
-    /**
-     * bits is not necessarily an AssertingMutableBits because index sorting needs to wrap it in a sorted view.
-     */
-    if (bits instanceof AssertingMutableBits) {
-      raw = (MutableBits) ((AssertingMutableBits) bits).in;
-    }
+    assert bits instanceof AssertingMutableBits;
+    MutableBits raw = (MutableBits) ((AssertingMutableBits)bits).in;
     check(raw, info.info.maxDoc(), info.getDelCount() + newDelCount);
     in.writeLiveDocs(raw, dir, info, newDelCount, context);
   }