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 7d96ff70e2241..94bd82934c769 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/Engine.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/Engine.java
@@ -132,6 +132,7 @@ public abstract class Engine implements Closeable {
     public static final String SEARCH_SOURCE = "search"; // TODO: Make source of search enum?
     public static final String CAN_MATCH_SEARCH_SOURCE = "can_match";
     protected static final String DOC_STATS_SOURCE = "doc_stats";
+    protected static final String SEGMENTS_STATS_SOURCE = "segments_stats";
     public static final long UNKNOWN_PRIMARY_TERM = -1L;
     public static final String ROOT_DOC_FIELD_NAME = "__root_doc_for_nested";
 
@@ -1136,7 +1137,7 @@ public SegmentsStats segmentsStats(boolean includeSegmentFileSizes, boolean incl
         ensureOpen();
         Set<String> segmentName = new HashSet<>();
         SegmentsStats stats = new SegmentsStats();
-        try (Searcher searcher = acquireSearcher("segments_stats", SearcherScope.INTERNAL)) {
+        try (Searcher searcher = acquireSearcher(SEGMENTS_STATS_SOURCE, SearcherScope.INTERNAL)) {
             for (LeafReaderContext ctx : searcher.getIndexReader().getContext().leaves()) {
                 SegmentReader segmentReader = Lucene.segmentReader(ctx.reader());
                 fillSegmentStats(segmentReader, includeSegmentFileSizes, stats);
@@ -1144,7 +1145,7 @@ public SegmentsStats segmentsStats(boolean includeSegmentFileSizes, boolean incl
             }
         }
 
-        try (Searcher searcher = acquireSearcher("segments_stats", SearcherScope.EXTERNAL)) {
+        try (Searcher searcher = acquireSearcher(SEGMENTS_STATS_SOURCE, SearcherScope.EXTERNAL)) {
             for (LeafReaderContext ctx : searcher.getIndexReader().getContext().leaves()) {
                 SegmentReader segmentReader = Lucene.segmentReader(ctx.reader());
                 if (segmentName.contains(segmentReader.getSegmentName()) == false) {
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 2358979995fd1..1e07acb1621c6 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
@@ -521,7 +521,7 @@ final boolean assertSearcherIsWarmedUp(String source, SearcherScope scope) {
             switch (source) {
                 // we can access segment_stats while a shard is still in the recovering state.
                 case "segments":
-                case "segments_stats":
+                case SEGMENTS_STATS_SOURCE:
                     break;
                 default:
                     assert externalReaderManager.isWarmedUp : "searcher was not warmed up yet for source[" + source + "]";
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/index/engine/frozen/FrozenEngine.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/index/engine/frozen/FrozenEngine.java
index 998603d8f4bc8..ece9ca080cd1d 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/index/engine/frozen/FrozenEngine.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/index/engine/frozen/FrozenEngine.java
@@ -250,7 +250,7 @@ private Engine.Searcher openSearcher(String source, SearcherScope scope) throws
             case "refresh_needed":
                 assert false : "refresh_needed is always false";
             case "segments":
-            case "segments_stats":
+            case SEGMENTS_STATS_SOURCE:
             case "completion_stats":
             case FIELD_RANGE_SEARCH_SOURCE: // special case for field_range - we use the cached point values reader
             case CAN_MATCH_SEARCH_SOURCE: // special case for can_match phase - we use the cached point values reader