diff --git a/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java b/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
index ffc18fc80..82af7db85 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
@@ -400,7 +400,7 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
         } else {
             // The previously used username, password and resource take over precedence over the
             // ones from the connection configuration
-            String username = usedUsername != null ? usedUsername : config.getUsername();
+            CharSequence username = usedUsername != null ? usedUsername : config.getUsername();
             String password = usedPassword != null ? usedPassword : config.getPassword();
             String resource = usedResource != null ? usedResource : config.getResource();
             login(username, password, resource);
@@ -408,7 +408,7 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
     }
 
     /**
-     * Same as {@link #login(String, String, String)}, but takes the resource from the connection
+     * Same as {@link #login(CharSequence, String, String)}, but takes the resource from the connection
      * configuration.
      * 
      * @param username
@@ -418,7 +418,7 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
      * @throws IOException
      * @see #login
      */
-    public synchronized void login(String username, String password) throws XMPPException, SmackException,
+    public synchronized void login(CharSequence username, String password) throws XMPPException, SmackException,
                     IOException {
         login(username, password, config.getResource());
     }
@@ -435,17 +435,17 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
      * @throws IOException
      * @see #login
      */
-    public synchronized void login(String username, String password, String resource) throws XMPPException,
+    public synchronized void login(CharSequence username, String password, String resource) throws XMPPException,
                     SmackException, IOException {
         if (!config.allowNullOrEmptyUsername && StringUtils.isNullOrEmpty(username)) {
             throw new IllegalArgumentException("Username must not be null or empty");
         }
         throwNotConnectedExceptionIfAppropriate();
         throwAlreadyLoggedInExceptionIfAppropriate();
-        usedUsername = username;
+        usedUsername = username != null ? username.toString() : null;
         usedPassword = password;
         usedResource = resource;
-        loginNonAnonymously(username, password, resource);
+        loginNonAnonymously(usedUsername, usedPassword, usedResource);
     }
 
     protected abstract void loginNonAnonymously(String username, String password, String resource)
diff --git a/smack-core/src/main/java/org/jivesoftware/smack/ConnectionConfiguration.java b/smack-core/src/main/java/org/jivesoftware/smack/ConnectionConfiguration.java
index fe269bc40..f8d4e9a6b 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/ConnectionConfiguration.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/ConnectionConfiguration.java
@@ -17,8 +17,6 @@
 
 package org.jivesoftware.smack;
 
-import java.util.Locale;
-
 import org.jivesoftware.smack.packet.Session;
 import org.jivesoftware.smack.proxy.ProxyInfo;
 import org.jivesoftware.smack.rosterstore.RosterStore;
@@ -65,7 +63,7 @@ public abstract class ConnectionConfiguration {
     // Holds the socket factory that is used to generate the socket in the connection
     private final SocketFactory socketFactory;
 
-    private final String username;
+    private final CharSequence username;
     private final String password;
     private final String resource;
     private final boolean sendPresence;
@@ -96,12 +94,7 @@ public abstract class ConnectionConfiguration {
     protected final boolean allowNullOrEmptyUsername;
 
     protected ConnectionConfiguration(Builder<?,?> builder) {
-        if (builder.username != null) {
-            // Do partial version of nameprep on the username.
-            username = builder.username.toLowerCase(Locale.US).trim();
-        } else {
-            username = null;
-        }
+        username = builder.username;
         password = builder.password;
         callbackHandler = builder.callbackHandler;
 
@@ -329,7 +322,7 @@ public abstract class ConnectionConfiguration {
      *
      * @return the username to use when trying to reconnect to the server.
      */
-    public String getUsername() {
+    public CharSequence getUsername() {
         return this.username;
     }
 
@@ -397,7 +390,7 @@ public abstract class ConnectionConfiguration {
         private String[] enabledSSLProtocols;
         private String[] enabledSSLCiphers;
         private HostnameVerifier hostnameVerifier;
-        private String username;
+        private CharSequence username;
         private String password;
         private String resource = "Smack";
         private boolean sendPresence = true;
@@ -427,7 +420,7 @@ public abstract class ConnectionConfiguration {
          * @param password the password or token used to authenticate
          * @return a reference to this builder.
          */
-        public B setUsernameAndPassword(String username, String password) {
+        public B setUsernameAndPassword(CharSequence username, String password) {
             this.username = username;
             this.password = password;
             return getThis();