diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index 30fa5f25da..4a420692a7 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -76,6 +76,9 @@ Trunk (unreleased changes)
 
     HADOOP-7965. Support for protocol version and signature in PB. (jitendra)
 
+    HADOOP-7988. Upper case in hostname part of the principals doesn't work with 
+    kerberos. (jitendra)
+
   BUGS
     HADOOP-7998. CheckFileSystem does not correctly honor setVerifyChecksum
                  (Daryn Sharp via bobby)
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/SecurityUtil.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/SecurityUtil.java
index a72b1f272c..abf9f3aa80 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/SecurityUtil.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/SecurityUtil.java
@@ -236,7 +236,7 @@ private static String replacePattern(String[] components, String hostname)
     if (fqdn == null || fqdn.equals("") || fqdn.equals("0.0.0.0")) {
       fqdn = getLocalHostName();
     }
-    return components[0] + "/" + fqdn + "@" + components[2];
+    return components[0] + "/" + fqdn.toLowerCase() + "@" + components[2];
   }
   
   static String getLocalHostName() throws UnknownHostException {
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/TestSecurityUtil.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/TestSecurityUtil.java
index 84f585b599..57a1e116de 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/TestSecurityUtil.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/TestSecurityUtil.java
@@ -89,6 +89,16 @@ public void testGetServerPrincipal() throws IOException {
     Mockito.verify(notUsed, Mockito.never()).getCanonicalHostName();
   }
 
+  @Test
+  public void testPrincipalsWithLowerCaseHosts() throws IOException {
+    String service = "xyz/";
+    String realm = "@REALM";
+    String principalInConf = service + SecurityUtil.HOSTNAME_PATTERN + realm;
+    String hostname = "FooHost";
+    String principal = service + hostname.toLowerCase() + realm;
+    verify(principalInConf, hostname, principal);
+  }
+
   @Test
   public void testLocalHostNameForNullOrWild() throws Exception {
     String local = SecurityUtil.getLocalHostName();