diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 603c986e73a..6cf590d9a67 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -236,6 +236,9 @@ Bug fixes
 * LUCENE-6586: Fix typo in GermanStemmer, causing possible wrong value
   for substCount.  (Christoph Kaser via Mike McCandless)
 
+* LUCENE-6658: Fix IndexUpgrader to also upgrade indexes without any
+  segments.  (Trejkaz, Uwe Schindler)
+
 Changes in Runtime Behavior
 
 * LUCENE-6501: The subreader structure in ParallelCompositeReader
diff --git a/lucene/backward-codecs/src/test/org/apache/lucene/index/TestBackwardsCompatibility.java b/lucene/backward-codecs/src/test/org/apache/lucene/index/TestBackwardsCompatibility.java
index 0b143f00229..dae837c1428 100644
--- a/lucene/backward-codecs/src/test/org/apache/lucene/index/TestBackwardsCompatibility.java
+++ b/lucene/backward-codecs/src/test/org/apache/lucene/index/TestBackwardsCompatibility.java
@@ -1118,6 +1118,7 @@ public class TestBackwardsCompatibility extends LuceneTestCase {
     for (SegmentCommitInfo si : infos) {
       assertEquals(Version.LATEST, si.info.getVersion());
     }
+    assertEquals(Version.LATEST, infos.getCommitLuceneVersion());
     return infos.size();
   }
   
@@ -1257,6 +1258,20 @@ public class TestBackwardsCompatibility extends LuceneTestCase {
     }
   }
 
+  public static final String emptyIndex = "empty.5.0.0.zip";
+
+  public void testUpgradeEmptyOldIndex() throws Exception {
+    Path oldIndexDir = createTempDir("emptyIndex");
+    TestUtil.unzip(getDataInputStream(emptyIndex), oldIndexDir);
+    Directory dir = newFSDirectory(oldIndexDir);
+
+    newIndexUpgrader(dir).upgrade();
+
+    checkAllSegmentsUpgraded(dir);
+    
+    dir.close();
+  }
+
   public static final String moreTermsIndex = "moreterms.5.0.0.zip";
 
   public void testMoreTerms() throws Exception {
diff --git a/lucene/backward-codecs/src/test/org/apache/lucene/index/empty.5.0.0.zip b/lucene/backward-codecs/src/test/org/apache/lucene/index/empty.5.0.0.zip
new file mode 100644
index 00000000000..473693ed23c
Binary files /dev/null and b/lucene/backward-codecs/src/test/org/apache/lucene/index/empty.5.0.0.zip differ
diff --git a/lucene/core/src/java/org/apache/lucene/index/IndexUpgrader.java b/lucene/core/src/java/org/apache/lucene/index/IndexUpgrader.java
index e7a6cba76a0..e8b2d52114f 100644
--- a/lucene/core/src/java/org/apache/lucene/index/IndexUpgrader.java
+++ b/lucene/core/src/java/org/apache/lucene/index/IndexUpgrader.java
@@ -52,6 +52,8 @@ import java.util.Collection;
   * documents.
   */
 public final class IndexUpgrader {
+  
+  private static final String LOG_PREFIX = "IndexUpgrader";
 
   @SuppressForbidden(reason = "System.out required: command line tool")
   private static void printUsage() {
@@ -162,18 +164,22 @@ public final class IndexUpgrader {
     iwc.setMergePolicy(new UpgradeIndexMergePolicy(iwc.getMergePolicy()));
     iwc.setIndexDeletionPolicy(new KeepOnlyLastCommitDeletionPolicy());
     
-    final IndexWriter w = new IndexWriter(dir, iwc);
-    try {
+    try (final IndexWriter w = new IndexWriter(dir, iwc)) {
       InfoStream infoStream = iwc.getInfoStream();
-      if (infoStream.isEnabled("IndexUpgrader")) {
-        infoStream.message("IndexUpgrader", "Upgrading all pre-" + Version.LATEST + " segments of index directory '" + dir + "' to version " + Version.LATEST + "...");
+      if (infoStream.isEnabled(LOG_PREFIX)) {
+        infoStream.message(LOG_PREFIX, "Upgrading all pre-" + Version.LATEST + " segments of index directory '" + dir + "' to version " + Version.LATEST + "...");
       }
       w.forceMerge(1);
-      if (infoStream.isEnabled("IndexUpgrader")) {
-        infoStream.message("IndexUpgrader", "All segments upgraded to version " + Version.LATEST);
+      if (infoStream.isEnabled(LOG_PREFIX)) {
+        infoStream.message(LOG_PREFIX, "All segments upgraded to version " + Version.LATEST);
+        infoStream.message(LOG_PREFIX, "Enforcing commit to rewrite all index metadata...");
+      }
+      w.setCommitData(w.getCommitData()); // fake change to enforce a commit (e.g. if index has no segments)
+      assert w.hasUncommittedChanges();
+      w.commit();
+      if (infoStream.isEnabled(LOG_PREFIX)) {
+        infoStream.message(LOG_PREFIX, "Committed upgraded metadata to index.");
       }
-    } finally {
-      w.close();
     }
   }