diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/main/java/org/apache/hadoop/yarn/server/webproxy/amfilter/AmFilterInitializer.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/main/java/org/apache/hadoop/yarn/server/webproxy/amfilter/AmFilterInitializer.java
index fa54c794a7d71..c3ddc54f3e25a 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/main/java/org/apache/hadoop/yarn/server/webproxy/amfilter/AmFilterInitializer.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/main/java/org/apache/hadoop/yarn/server/webproxy/amfilter/AmFilterInitializer.java
@@ -62,15 +62,19 @@ public void initFilter(FilterContainer container, Configuration conf) {
     container.addFilter(FILTER_NAME, FILTER_CLASS, params);
 
     // Handle RM HA urls
-    List<String> urls = new ArrayList<>();
-
     // Include yarn-site.xml in the classpath
     YarnConfiguration yarnConf = new YarnConfiguration(conf);
-    for (String rmId : getRmIds(yarnConf)) {
-      String url = getUrlByRmId(yarnConf, rmId);
-      urls.add(url);
+    Collection<String> rmIds = getRmIds(yarnConf);
+    if (rmIds != null) {
+      List<String> urls = new ArrayList<>();
+      for (String rmId : rmIds) {
+        String url = getUrlByRmId(yarnConf, rmId);
+        urls.add(url);
+      }
+      if (!urls.isEmpty()) {
+        params.put(RM_HA_URLS, StringUtils.join(",", urls));
+      }
     }
-    params.put(RM_HA_URLS, StringUtils.join(",", urls));
   }
 
   private Collection<String> getRmIds(Configuration conf) {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/test/java/org/apache/hadoop/yarn/server/webproxy/amfilter/TestAmFilterInitializer.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/test/java/org/apache/hadoop/yarn/server/webproxy/amfilter/TestAmFilterInitializer.java
index b621012099b61..97625ac0882b0 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/test/java/org/apache/hadoop/yarn/server/webproxy/amfilter/TestAmFilterInitializer.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-web-proxy/src/test/java/org/apache/hadoop/yarn/server/webproxy/amfilter/TestAmFilterInitializer.java
@@ -56,11 +56,11 @@ public void testInitFilter() {
     AmFilterInitializer afi = new MockAmFilterInitializer();
     assertNull(con.givenParameters);
     afi.initFilter(con, conf);
-    assertEquals(3, con.givenParameters.size());
+    assertEquals(2, con.givenParameters.size());
     assertEquals("host1", con.givenParameters.get(AmIpFilter.PROXY_HOSTS));
     assertEquals("http://host1:1000/foo",
         con.givenParameters.get(AmIpFilter.PROXY_URI_BASES));
-    assertEquals("", con.givenParameters.get(AmFilterInitializer.RM_HA_URLS));
+    assertEquals(null, con.givenParameters.get(AmFilterInitializer.RM_HA_URLS));
 
     // Check a single RM_WEBAPP_ADDRESS
     con = new MockFilterContainer();
@@ -69,11 +69,11 @@ public void testInitFilter() {
     afi = new MockAmFilterInitializer();
     assertNull(con.givenParameters);
     afi.initFilter(con, conf);
-    assertEquals(3, con.givenParameters.size());
+    assertEquals(2, con.givenParameters.size());
     assertEquals("host2", con.givenParameters.get(AmIpFilter.PROXY_HOSTS));
     assertEquals("http://host2:2000/foo",
         con.givenParameters.get(AmIpFilter.PROXY_URI_BASES));
-    assertEquals("", con.givenParameters.get(AmFilterInitializer.RM_HA_URLS));
+    assertEquals(null, con.givenParameters.get(AmFilterInitializer.RM_HA_URLS));
 
     // Check multiple RM_WEBAPP_ADDRESSes (RM HA)
     con = new MockFilterContainer();