diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/RMWebServices.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/RMWebServices.java
index 9f8d0b9bd7a..02d9cfa50ca 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/RMWebServices.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/RMWebServices.java
@@ -31,6 +31,7 @@ import java.util.Collections;
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -2391,14 +2392,22 @@ public class RMWebServices extends WebServices implements RMWebServiceProtocol {
                 ((MutableConfScheduler) scheduler).getMutableConfProvider();
         Configuration schedulerConf = mutableConfigurationProvider
                 .getConfiguration();
-        Configuration newConfig = mutableConfigurationProvider
+        Configuration newSchedulerConf = mutableConfigurationProvider
                 .applyChanges(schedulerConf, mutationInfo);
         Configuration yarnConf = ((CapacityScheduler) scheduler).getConf();
+
+        Configuration newConfig = new Configuration(yarnConf);
+        Iterator<Map.Entry<String, String>> iter = newSchedulerConf.iterator();
+        Entry<String, String> e = null;
+        while (iter.hasNext()) {
+          e = iter.next();
+          newConfig.set(e.getKey(), e.getValue());
+        }
         CapacitySchedulerConfigValidator.validateCSConfiguration(yarnConf,
                 newConfig, rm.getRMContext());
 
         return Response.status(Status.OK)
-                .entity(new ConfInfo(newConfig))
+                .entity(new ConfInfo(newSchedulerConf))
                 .build();
       } catch (Exception e) {
         String errorMsg = "CapacityScheduler configuration validation failed:"
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/TestRMWebServicesConfigurationMutation.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/TestRMWebServicesConfigurationMutation.java
index e2f82a03031..d12c2fffe94 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/TestRMWebServicesConfigurationMutation.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/TestRMWebServicesConfigurationMutation.java
@@ -731,6 +731,32 @@ public class TestRMWebServicesConfigurationMutation extends JerseyTestBase {
         newCSConf.getMaximumSystemApplications());
   }
 
+  @Test
+  public void testValidateWithClusterMaxAllocation() throws Exception {
+    WebResource r = resource();
+    int clusterMax = YarnConfiguration.
+        DEFAULT_RM_SCHEDULER_MAXIMUM_ALLOCATION_MB * 2;
+    conf.setInt(YarnConfiguration.RM_SCHEDULER_MAXIMUM_ALLOCATION_MB,
+        clusterMax);
+
+    SchedConfUpdateInfo updateInfo = new SchedConfUpdateInfo();
+    Map<String, String> updateParam = new HashMap<>();
+    updateParam.put(CapacitySchedulerConfiguration.MAXIMUM_APPLICATIONS_SUFFIX,
+        "100");
+    QueueConfigInfo aUpdateInfo = new QueueConfigInfo("root.a", updateParam);
+    updateInfo.getUpdateQueueInfo().add(aUpdateInfo);
+
+    ClientResponse response =
+        r.path("ws").path("v1").path("cluster")
+            .path(RMWSConsts.SCHEDULER_CONF_VALIDATE)
+            .queryParam("user.name", userName)
+            .accept(MediaType.APPLICATION_JSON)
+            .entity(YarnWebServiceUtils.toJson(updateInfo,
+                SchedConfUpdateInfo.class), MediaType.APPLICATION_JSON)
+            .post(ClientResponse.class);
+    assertEquals(Status.OK.getStatusCode(), response.getStatus());
+  }
+
   @Override
   @After
   public void tearDown() throws Exception {