diff --git a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/metrics/NamenodeBeanMetrics.java b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/metrics/NamenodeBeanMetrics.java
index 45ae81ed063f5..0e6e12a0d3e14 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/metrics/NamenodeBeanMetrics.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/metrics/NamenodeBeanMetrics.java
@@ -855,7 +855,7 @@ public long getNumberOfSnapshottableDirs() {
 
   @Override
   public String getEnteringMaintenanceNodes() {
-    return "N/A";
+    return "{}";
   }
 
   @Override
diff --git a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterRpc.java b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterRpc.java
index a7c002566482d..c3e7f10c95a00 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterRpc.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterRpc.java
@@ -1748,6 +1748,14 @@ public void testRBFMetricsMethodsRelayOnStateStore() {
     assertEquals(0, metrics.getNumLiveNodes());
   }
 
+  @Test
+  public void testNamenodeMetricsEnteringMaintenanceNodes() throws IOException {
+    final NamenodeBeanMetrics metrics =
+            router.getRouter().getNamenodeMetrics();
+
+    assertEquals("{}", metrics.getEnteringMaintenanceNodes());
+  }
+
   @Test
   public void testCacheAdmin() throws Exception {
     DistributedFileSystem routerDFS = (DistributedFileSystem) routerFS;