diff --git a/spring-security-kerberos-client/src/main/java/org/springframework/security/kerberos/client/KerberosRestTemplate.java b/spring-security-kerberos-client/src/main/java/org/springframework/security/kerberos/client/KerberosRestTemplate.java
index 8aa2b31..fe2b278 100644
--- a/spring-security-kerberos-client/src/main/java/org/springframework/security/kerberos/client/KerberosRestTemplate.java
+++ b/spring-security-kerberos-client/src/main/java/org/springframework/security/kerberos/client/KerberosRestTemplate.java
@@ -214,7 +214,9 @@ private static HttpClient buildHttpClient() {
 	private LoginContext buildLoginContext() throws LoginException {
 		ClientLoginConfig loginConfig = new ClientLoginConfig(keyTabLocation, userPrincipal, password, loginOptions);
 		Set<Principal> princ = new HashSet<Principal>(1);
-		princ.add(new KerberosPrincipal(userPrincipal));
+		if (userPrincipal != null) {
+			princ.add(new KerberosPrincipal(userPrincipal));
+		}
 		Subject sub = new Subject(false, princ, new HashSet<Object>(), new HashSet<Object>());
 		CallbackHandler callbackHandler = new CallbackHandlerImpl(userPrincipal, password);
 		LoginContext lc = new LoginContext("", sub, callbackHandler, loginConfig);