diff --git a/server/src/main/java/org/elasticsearch/index/engine/Engine.java b/server/src/main/java/org/elasticsearch/index/engine/Engine.java
index f50f88456a5..d70603e0370 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/Engine.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/Engine.java
@@ -110,6 +110,7 @@ public abstract class Engine implements Closeable {
     public static final String SYNC_COMMIT_ID = "sync_id";
     public static final String HISTORY_UUID_KEY = "history_uuid";
     public static final String MIN_RETAINED_SEQNO = "min_retained_seq_no";
+    public static final String MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID = "max_unsafe_auto_id_timestamp";
 
     protected final ShardId shardId;
     protected final String allocationId;
diff --git a/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java b/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
index 955fd2bec41..5bd1a473fb9 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
@@ -139,7 +139,6 @@ public class InternalEngine extends Engine {
     // incoming indexing ops to a single thread:
     private final AtomicInteger throttleRequestCount = new AtomicInteger();
     private final AtomicBoolean pendingTranslogRecovery = new AtomicBoolean(false);
-    public static final String MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID = "max_unsafe_auto_id_timestamp";
     private final AtomicLong maxUnsafeAutoIdTimestamp = new AtomicLong(-1);
     private final AtomicLong maxSeenAutoIdTimestamp = new AtomicLong(-1);
     private final AtomicLong maxSeqNoOfNonAppendOnlyOperations = new AtomicLong(SequenceNumbers.NO_OPS_PERFORMED);
diff --git a/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java b/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
index f28db00ac8a..28ff3c93096 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
@@ -79,7 +79,6 @@ import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineConfig;
 import org.elasticsearch.index.engine.EngineException;
 import org.elasticsearch.index.engine.EngineFactory;
-import org.elasticsearch.index.engine.InternalEngine;
 import org.elasticsearch.index.engine.RefreshFailedEngineException;
 import org.elasticsearch.index.engine.Segment;
 import org.elasticsearch.index.engine.SegmentsStats;
@@ -1399,8 +1398,8 @@ public class IndexShard extends AbstractIndexShardComponent implements IndicesCl
 
     private boolean assertMaxUnsafeAutoIdInCommit() throws IOException {
         final Map<String, String> userData = SegmentInfos.readLatestCommit(store.directory()).getUserData();
-        assert userData.containsKey(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID) :
-            "opening index which was created post 5.5.0 but " + InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID
+        assert userData.containsKey(Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID) :
+            "opening index which was created post 5.5.0 but " + Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID
                 + " is not found in commit";
         return true;
     }
diff --git a/server/src/main/java/org/elasticsearch/index/shard/LocalShardSnapshot.java b/server/src/main/java/org/elasticsearch/index/shard/LocalShardSnapshot.java
index 09391c9bc96..cc9ac40c274 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/LocalShardSnapshot.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/LocalShardSnapshot.java
@@ -28,7 +28,6 @@ import org.apache.lucene.store.NoLockFactory;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.engine.Engine;
-import org.elasticsearch.index.engine.InternalEngine;
 import org.elasticsearch.index.store.Store;
 
 import java.io.Closeable;
@@ -66,7 +65,7 @@ final class LocalShardSnapshot implements Closeable {
     }
 
     long maxUnsafeAutoIdTimestamp() {
-        return Long.parseLong(shard.getEngine().commitStats().getUserData().get(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID));
+        return Long.parseLong(shard.getEngine().commitStats().getUserData().get(Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID));
     }
 
     Directory getSnapshotDirectory() {
diff --git a/server/src/main/java/org/elasticsearch/index/shard/StoreRecovery.java b/server/src/main/java/org/elasticsearch/index/shard/StoreRecovery.java
index c4b971e470d..4d8b63fc719 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/StoreRecovery.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/StoreRecovery.java
@@ -40,8 +40,8 @@ import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.index.Index;
+import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineException;
-import org.elasticsearch.index.engine.InternalEngine;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.seqno.SequenceNumbers;
 import org.elasticsearch.index.snapshots.IndexShardRestoreFailedException;
@@ -181,7 +181,7 @@ final class StoreRecovery {
                 final HashMap<String, String> liveCommitData = new HashMap<>(3);
                 liveCommitData.put(SequenceNumbers.MAX_SEQ_NO, Long.toString(maxSeqNo));
                 liveCommitData.put(SequenceNumbers.LOCAL_CHECKPOINT_KEY, Long.toString(maxSeqNo));
-                liveCommitData.put(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, Long.toString(maxUnsafeAutoIdTimestamp));
+                liveCommitData.put(Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, Long.toString(maxUnsafeAutoIdTimestamp));
                 return liveCommitData.entrySet().iterator();
             });
             writer.commit();
diff --git a/server/src/main/java/org/elasticsearch/index/store/Store.java b/server/src/main/java/org/elasticsearch/index/store/Store.java
index ddd642a2f0f..13499dfd60c 100644
--- a/server/src/main/java/org/elasticsearch/index/store/Store.java
+++ b/server/src/main/java/org/elasticsearch/index/store/Store.java
@@ -75,7 +75,6 @@ import org.elasticsearch.env.ShardLockObtainFailedException;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.engine.CombinedDeletionPolicy;
 import org.elasticsearch.index.engine.Engine;
-import org.elasticsearch.index.engine.InternalEngine;
 import org.elasticsearch.index.seqno.SequenceNumbers;
 import org.elasticsearch.index.shard.AbstractIndexShardComponent;
 import org.elasticsearch.index.shard.IndexShard;
@@ -1425,7 +1424,7 @@ public class Store extends AbstractIndexShardComponent implements Closeable, Ref
             map.put(Engine.HISTORY_UUID_KEY, UUIDs.randomBase64UUID());
             map.put(SequenceNumbers.LOCAL_CHECKPOINT_KEY, Long.toString(SequenceNumbers.NO_OPS_PERFORMED));
             map.put(SequenceNumbers.MAX_SEQ_NO, Long.toString(SequenceNumbers.NO_OPS_PERFORMED));
-            map.put(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, "-1");
+            map.put(Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID, "-1");
             updateCommitData(writer, map);
         } finally {
             metadataLock.writeLock().unlock();
diff --git a/server/src/test/java/org/elasticsearch/index/shard/StoreRecoveryTests.java b/server/src/test/java/org/elasticsearch/index/shard/StoreRecoveryTests.java
index 9a889801c6c..8b606c82b1b 100644
--- a/server/src/test/java/org/elasticsearch/index/shard/StoreRecoveryTests.java
+++ b/server/src/test/java/org/elasticsearch/index/shard/StoreRecoveryTests.java
@@ -44,7 +44,7 @@ import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.cluster.routing.OperationRouting;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.index.engine.InternalEngine;
+import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.mapper.IdFieldMapper;
 import org.elasticsearch.index.mapper.Uid;
 import org.elasticsearch.index.seqno.SequenceNumbers;
@@ -118,7 +118,7 @@ public class StoreRecoveryTests extends ESTestCase {
         final Map<String, String> userData = segmentCommitInfos.getUserData();
         assertThat(userData.get(SequenceNumbers.MAX_SEQ_NO), equalTo(Long.toString(maxSeqNo)));
         assertThat(userData.get(SequenceNumbers.LOCAL_CHECKPOINT_KEY), equalTo(Long.toString(maxSeqNo)));
-        assertThat(userData.get(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID), equalTo(Long.toString(maxUnsafeAutoIdTimestamp)));
+        assertThat(userData.get(Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID), equalTo(Long.toString(maxUnsafeAutoIdTimestamp)));
         for (SegmentCommitInfo info : segmentCommitInfos) { // check that we didn't merge
             assertEquals("all sources must be flush",
                 info.info.getDiagnostics().get("source"), "flush");
@@ -179,7 +179,7 @@ public class StoreRecoveryTests extends ESTestCase {
         final Map<String, String> userData = segmentCommitInfos.getUserData();
         assertThat(userData.get(SequenceNumbers.MAX_SEQ_NO), equalTo(Long.toString(maxSeqNo)));
         assertThat(userData.get(SequenceNumbers.LOCAL_CHECKPOINT_KEY), equalTo(Long.toString(maxSeqNo)));
-        assertThat(userData.get(InternalEngine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID), equalTo(Long.toString(maxUnsafeAutoIdTimestamp)));
+        assertThat(userData.get(Engine.MAX_UNSAFE_AUTO_ID_TIMESTAMP_COMMIT_ID), equalTo(Long.toString(maxUnsafeAutoIdTimestamp)));
         for (SegmentCommitInfo info : segmentCommitInfos) { // check that we didn't merge
             assertEquals("all sources must be flush",
                 info.info.getDiagnostics().get("source"), "flush");