diff --git a/core/src/main/java/org/elasticsearch/index/engine/InternalEngine.java b/core/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
index 01f02025aeb..dc0669e02b7 100644
--- a/core/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
+++ b/core/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
@@ -743,7 +743,9 @@ public class InternalEngine extends Engine {
                     indexWriter.forceMerge(maxNumSegments, true /* blocks and waits for merges*/);
                 }
                 if (flush) {
-                    flush(true, true);
+                    if (tryRenewSyncCommit() == false) {
+                        flush(false, true);
+                    }
                 }
                 if (upgrade) {
                     logger.info("finished segment upgrade");
diff --git a/core/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java b/core/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java
index e9971a15f8e..abe0851c2b6 100644
--- a/core/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java
+++ b/core/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java
@@ -485,7 +485,7 @@ public class InternalEngineTests extends ESTestCase {
 
             if (flush) {
                 // we should have had just 1 merge, so last generation should be exact
-                assertEquals(gen2 + 1, store.readLastCommittedSegmentsInfo().getLastGeneration());
+                assertEquals(gen2, store.readLastCommittedSegmentsInfo().getLastGeneration());
             }
         }
     }
@@ -843,7 +843,7 @@ public class InternalEngineTests extends ESTestCase {
                         Engine.SyncedFlushResult.SUCCESS);
                 assertEquals(3, engine.segments(false).size());
 
-                engine.forceMerge(false, 1, false, false, false);
+                engine.forceMerge(forceMergeFlushes, 1, false, false, false);
                 if (forceMergeFlushes == false) {
                     engine.refresh("make all segments visible");
                     assertEquals(4, engine.segments(false).size());