diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
index 0510abd043..e4d01a1a23 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
@@ -1678,10 +1678,7 @@ public static UserGroupInformation createProxyUserForTesting(String user,
    * @return the user's name up to the first '/' or '@'.
    */
   public String getShortUserName() {
-    for (User p: subject.getPrincipals(User.class)) {
-      return p.getShortName();
-    }
-    return null;
+    return user.getShortName();
   }
 
   public String getPrimaryGroupName() throws IOException {