diff --git a/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/wsrs/UserProvider.java b/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/wsrs/UserProvider.java
index 4db42c21ac8..fd59b19dc34 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/wsrs/UserProvider.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/wsrs/UserProvider.java
@@ -53,10 +53,9 @@ public class UserProvider extends AbstractHttpContextInjectable<Principal> imple
     public String parseParam(String str) {
       if (str != null) {
         int len = str.length();
-        if (len < 1 || len > 31) {
+        if (len < 1) {
           throw new IllegalArgumentException(MessageFormat.format(
-            "Parameter [{0}], invalid value [{1}], it's length must be between 1 and 31",
-            getName(), str));
+            "Parameter [{0}], it's length must be at least 1", getName()));
         }
       }
       return super.parseParam(str);
diff --git a/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/test/java/org/apache/hadoop/lib/wsrs/TestUserProvider.java b/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/test/java/org/apache/hadoop/lib/wsrs/TestUserProvider.java
index 2bba4f090d0..694e8dc3185 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/test/java/org/apache/hadoop/lib/wsrs/TestUserProvider.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/test/java/org/apache/hadoop/lib/wsrs/TestUserProvider.java
@@ -108,13 +108,6 @@ public class TestUserProvider {
     userParam.parseParam("");
   }
 
-  @Test
-  @TestException(exception = IllegalArgumentException.class)
-  public void userNameTooLong() {
-    UserProvider.UserParam userParam = new UserProvider.UserParam("username");
-    userParam.parseParam("a123456789012345678901234567890x");
-  }
-
   @Test
   @TestException(exception = IllegalArgumentException.class)
   public void userNameInvalidStart() {
@@ -135,12 +128,6 @@ public class TestUserProvider {
     assertNotNull(userParam.parseParam("a"));
   }
 
-  @Test
-  public void userNameMaxLength() {
-    UserProvider.UserParam userParam = new UserProvider.UserParam("username");
-    assertNotNull(userParam.parseParam("a123456789012345678901234567890"));
-  }
-
   @Test
   public void userNameValidDollarSign() {
     UserProvider.UserParam userParam = new UserProvider.UserParam("username");
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 6dc804e25f0..967f4684755 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -303,6 +303,9 @@ Release 2.0.3-alpha - Unreleased
     HDFS-4282. TestEditLog.testFuzzSequences FAILED in all pre-commit test
     (todd)
 
+    HDFS-4236. Remove artificial limit on username length introduced in
+    HDFS-4171. (tucu via suresh)
+
   BREAKDOWN OF HDFS-3077 SUBTASKS
 
     HDFS-3077. Quorum-based protocol for reading and writing edit logs.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/resources/UserParam.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/resources/UserParam.java
index ead8e54882b..36e128feedb 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/resources/UserParam.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/resources/UserParam.java
@@ -38,10 +38,9 @@ public class UserParam extends StringParam {
         MessageFormat.format("Parameter [{0}], cannot be NULL", NAME));
     }
     int len = str.length();
-    if (len < 1 || len > 31) {
+    if (len < 1) {
       throw new IllegalArgumentException(MessageFormat.format(
-        "Parameter [{0}], invalid value [{1}], it's length must be between 1 and 31",
-        NAME, str));
+        "Parameter [{0}], it's length must be at least 1", NAME));
     }
     return str;
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/resources/TestParam.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/resources/TestParam.java
index 0e06de319ad..c228c1f2989 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/resources/TestParam.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/resources/TestParam.java
@@ -244,11 +244,6 @@ public class TestParam {
     assertNull(userParam.getValue());
   }
 
-  @Test(expected = IllegalArgumentException.class)
-  public void userNameTooLong() {
-    new UserParam("a123456789012345678901234567890x");
-  }
-
   @Test(expected = IllegalArgumentException.class)
   public void userNameInvalidStart() {
     new UserParam("1x");
@@ -265,12 +260,6 @@ public class TestParam {
     assertNotNull(userParam.getValue());
   }
 
-  @Test
-  public void userNameMaxLength() {
-    UserParam userParam = new UserParam("a123456789012345678901234567890");
-    assertNotNull(userParam.getValue());
-  }
-
   @Test
   public void userNameValidDollarSign() {
     UserParam userParam = new UserParam("a$");