diff --git a/server/src/main/java/org/opensearch/index/mapper/ConstantKeywordFieldMapper.java b/server/src/main/java/org/opensearch/index/mapper/ConstantKeywordFieldMapper.java
index f2f2e1e12a046..cafea3937310d 100644
--- a/server/src/main/java/org/opensearch/index/mapper/ConstantKeywordFieldMapper.java
+++ b/server/src/main/java/org/opensearch/index/mapper/ConstantKeywordFieldMapper.java
@@ -97,6 +97,7 @@ public ConstantKeywordFieldMapper build(BuilderContext context) {
      *
      * @opensearch.internal
      */
+    @PublicApi(since = "2.14.0")
     static final class ConstantKeywordFieldType extends ConstantFieldType {
 
         protected final String value;