diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 1ee488d6df6..18b93789805 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -589,6 +589,9 @@ Release 2.0.0 - UNRELEASED
     HDFS-3330. If GetImageServlet throws an Error or RTE, response should not
     have HTTP "OK" status. (todd)
 
+    HDFS-3351. NameNode#initializeGenericKeys should always set fs.defaultFS
+    regardless of whether HA or Federation is enabled. (atm)
+
   BREAKDOWN OF HDFS-1623 SUBTASKS
 
     HDFS-2179. Add fencing framework and mechanisms for NameNode HA. (todd)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
index 48a056507c4..05bc8c2ec67 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
@@ -1130,20 +1130,18 @@ public class NameNode {
    */
   public static void initializeGenericKeys(Configuration conf,
       String nameserviceId, String namenodeId) {
-    if ((nameserviceId == null || nameserviceId.isEmpty()) && 
-        (namenodeId == null || namenodeId.isEmpty())) {
-      return;
+    if ((nameserviceId != null && !nameserviceId.isEmpty()) || 
+        (namenodeId != null && !namenodeId.isEmpty())) {
+      if (nameserviceId != null) {
+        conf.set(DFS_FEDERATION_NAMESERVICE_ID, nameserviceId);
+      }
+      if (namenodeId != null) {
+        conf.set(DFS_HA_NAMENODE_ID_KEY, namenodeId);
+      }
+      
+      DFSUtil.setGenericConf(conf, nameserviceId, namenodeId,
+          NAMESERVICE_SPECIFIC_KEYS);
     }
-    
-    if (nameserviceId != null) {
-      conf.set(DFS_FEDERATION_NAMESERVICE_ID, nameserviceId);
-    }
-    if (namenodeId != null) {
-      conf.set(DFS_HA_NAMENODE_ID_KEY, namenodeId);
-    }
-    
-    DFSUtil.setGenericConf(conf, nameserviceId, namenodeId,
-        NAMESERVICE_SPECIFIC_KEYS);
     if (conf.get(DFS_NAMENODE_RPC_ADDRESS_KEY) != null) {
       URI defaultUri = URI.create(HdfsConstants.HDFS_URI_SCHEME + "://"
           + conf.get(DFS_NAMENODE_RPC_ADDRESS_KEY));
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSUtil.java
index 3f1421e872f..a991d37c8a3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSUtil.java
@@ -319,6 +319,25 @@ public class TestDFSUtil {
     }
   }
 
+  /**
+   * Ensure that fs.defaultFS is set in the configuration even if neither HA nor
+   * Federation is enabled.
+   * 
+   * Regression test for HDFS-3351.
+   */
+  @Test
+  public void testConfModificationNoFederationOrHa() {
+    final HdfsConfiguration conf = new HdfsConfiguration();
+    String nsId = null;
+    String nnId = null;
+    
+    conf.set(DFS_NAMENODE_RPC_ADDRESS_KEY, "localhost:1234");
+
+    assertFalse("hdfs://localhost:1234".equals(conf.get(FS_DEFAULT_NAME_KEY)));
+    NameNode.initializeGenericKeys(conf, nsId, nnId);
+    assertEquals("hdfs://localhost:1234", conf.get(FS_DEFAULT_NAME_KEY));
+  }
+
   /**
    * Regression test for HDFS-2934.
    */