diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index e81fad302dc..cc022273484 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -96,7 +96,6 @@ Other
   perform as well as other options.  (Robert Muir)
 
 ======================= Lucene 4.11.0 ======================
-(No Changes)
 
 New Features
 
@@ -106,6 +105,11 @@ New Features
 * LUCENE-5889: Add commit method to AnalyzingInfixSuggester, and allow just using .add
   to build up the suggester.  (Varun Thacker via Mike McCandless)
 
+Bug Fixes
+
+* LUCENE-5672: IndexWriter.addIndexes() calls maybeMerge(), to ensure the index stays
+  healthy. If you don't want merging use NoMergePolicy instead. (Robert Muir)
+
 ======================= Lucene 4.10.0 ======================
 
 New Features
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 cf5d22778dc..7f076ec0291 100644
--- a/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
@@ -2388,11 +2388,6 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable {
    * free space required will be higher by the size of the
    * starting index (see {@link #forceMerge(int)} for details).
    *
-   * <p>
-   * <b>NOTE:</b> this method only copies the segments of the incoming indexes
-   * and does not merge them. Therefore deleted documents are not removed and
-   * the new segments are not merged with the existing ones.
-   *
    * <p>This requires this index not be among those to be added.
    *
    * <p>
@@ -2499,6 +2494,7 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable {
         IOUtils.closeWhileHandlingException(locks);
       }
     }
+    maybeMerge();
   }
   
   /**
@@ -2654,6 +2650,7 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable {
     } catch (OutOfMemoryError oom) {
       handleOOM(oom, "addIndexes(IndexReader...)");
     }
+    maybeMerge();
   }
 
   /** Copies the segment files as-is into the IndexWriter's directory. */