diff --git a/besu/src/main/java/org/hyperledger/besu/services/BlockchainServiceImpl.java b/besu/src/main/java/org/hyperledger/besu/services/BlockchainServiceImpl.java
index 810b4ec3c7..a3b37a6665 100644
--- a/besu/src/main/java/org/hyperledger/besu/services/BlockchainServiceImpl.java
+++ b/besu/src/main/java/org/hyperledger/besu/services/BlockchainServiceImpl.java
@@ -17,6 +17,7 @@ package org.hyperledger.besu.services;
 
 import org.hyperledger.besu.ethereum.chain.Blockchain;
 import org.hyperledger.besu.ethereum.core.BlockBody;
+import org.hyperledger.besu.plugin.Unstable;
 import org.hyperledger.besu.plugin.data.BlockContext;
 import org.hyperledger.besu.plugin.data.BlockHeader;
 import org.hyperledger.besu.plugin.services.BlockchainService;
@@ -25,6 +26,7 @@ import java.util.Optional;
 import java.util.function.Supplier;
 
 /** The Blockchain service implementation. */
+@Unstable
 public class BlockchainServiceImpl implements BlockchainService {
 
   private final Blockchain blockchain;
diff --git a/plugin-api/build.gradle b/plugin-api/build.gradle
index 3237a5076f..a389fde870 100644
--- a/plugin-api/build.gradle
+++ b/plugin-api/build.gradle
@@ -67,7 +67,7 @@ Calculated : ${currentHash}
 tasks.register('checkAPIChanges', FileStateChecker) {
   description = "Checks that the API for the Plugin-API project does not change without deliberate thought"
   files = sourceSets.main.allJava.files
-  knownHash = 'VFMEmmE/7EyfKVpNhcK7KxMn0s5muPP4lorhW5iTuxo='
+  knownHash = 'vFAmK8jMtMc9nJaoeyPn76jDPFbwnogqQTVAOg3TSP4='
 }
 check.dependsOn('checkAPIChanges')
 
diff --git a/plugin-api/src/main/java/org/hyperledger/besu/plugin/services/BlockchainService.java b/plugin-api/src/main/java/org/hyperledger/besu/plugin/services/BlockchainService.java
index 38eeb99875..e9356ae76e 100644
--- a/plugin-api/src/main/java/org/hyperledger/besu/plugin/services/BlockchainService.java
+++ b/plugin-api/src/main/java/org/hyperledger/besu/plugin/services/BlockchainService.java
@@ -14,11 +14,13 @@
  */
 package org.hyperledger.besu.plugin.services;
 
+import org.hyperledger.besu.plugin.Unstable;
 import org.hyperledger.besu.plugin.data.BlockContext;
 
 import java.util.Optional;
 
 /** A service that plugins can use to query blocks by number */
+@Unstable
 public interface BlockchainService extends BesuService {
   /**
    * Gets block by number