diff --git a/phpBB/includes/acp/acp_users.php b/phpBB/includes/acp/acp_users.php
index ae64fd37ed..dc08a766a3 100644
--- a/phpBB/includes/acp/acp_users.php
+++ b/phpBB/includes/acp/acp_users.php
@@ -790,7 +790,7 @@ class acp_users
 					$error = preg_replace('#^([A-Z_]+)$#e', "(!empty(\$user->lang['\\1'])) ? \$user->lang['\\1'] : '\\1'", $error);
 				}
 
-				$user_char_ary = array('.*' => 'USERNAME_CHARS_ANY', '[\w]+' => 'USERNAME_ALPHA_ONLY', '[\w_\+\. \-\[\]]+' => 'USERNAME_ALPHA_SPACERS');
+				$user_char_ary = array('.*' => 'USERNAME_CHARS_ANY', '[a-z]+' => 'USERNAME_ALPHA_ONLY', '[-\]_+ [a-z]+' => 'USERNAME_ALPHA_SPACERS', '\w+' => 'USERNAME_LETTER_NUM', '[-\]_+ [\w]+' => 'USERNAME_LETTER_NUM_SPACERS');
 				$pass_char_ary = array('.*' => 'PASS_TYPE_ANY', '[a-zA-Z]' => 'PASS_TYPE_CASE', '[a-zA-Z0-9]' => 'PASS_TYPE_ALPHA', '[a-zA-Z\W]' => 'PASS_TYPE_SYMBOL');
 
 				if ($user_id == $user->data['user_id'])
diff --git a/phpBB/includes/functions_user.php b/phpBB/includes/functions_user.php
index 1d11f00298..a8fb455cdf 100644
--- a/phpBB/includes/functions_user.php
+++ b/phpBB/includes/functions_user.php
@@ -1148,7 +1148,7 @@ function validate_username($username)
 		return false;
 	}
 
-	if (!preg_match('#^' . str_replace('\\\\', '\\', $config['allow_name_chars']) . '$#i', $username) || strpos($username, '"') !== false || strpos($username, '"') !== false)
+	if (!preg_match('#^' . str_replace('\\\\', '\\', $config['allow_name_chars']) . '$#ui', $username) || strpos($username, '"') !== false || strpos($username, '"') !== false)
 	{
 		return 'INVALID_CHARS';
 	}
diff --git a/phpBB/includes/ucp/ucp_register.php b/phpBB/includes/ucp/ucp_register.php
index b8d5c438a7..37d44958bc 100644
--- a/phpBB/includes/ucp/ucp_register.php
+++ b/phpBB/includes/ucp/ucp_register.php
@@ -478,7 +478,7 @@ class ucp_register
 			break;
 		}
 
-		$user_char_ary = array('.*' => 'USERNAME_CHARS_ANY', '[\w]+' => 'USERNAME_ALPHA_ONLY', '[\w_\+\. \-\[\]]+' => 'USERNAME_ALPHA_SPACERS');
+		$user_char_ary = array('.*' => 'USERNAME_CHARS_ANY', '[a-z]+' => 'USERNAME_ALPHA_ONLY', '[-\]_+ [a-z]+' => 'USERNAME_ALPHA_SPACERS', '\w+' => 'USERNAME_LETTER_NUM', '[-\]_+ [\w]+' => 'USERNAME_LETTER_NUM_SPACERS');
 		$pass_char_ary = array('.*' => 'PASS_TYPE_ANY', '[a-zA-Z]' => 'PASS_TYPE_CASE', '[a-zA-Z0-9]' => 'PASS_TYPE_ALPHA', '[a-zA-Z\W]' => 'PASS_TYPE_SYMBOL');
 
 		//
diff --git a/phpBB/install/database_update.php b/phpBB/install/database_update.php
index 97cf8ad8b6..febd88665f 100644
--- a/phpBB/install/database_update.php
+++ b/phpBB/install/database_update.php
@@ -569,6 +569,17 @@ if (version_compare($current_version, '3.0.b4', '<='))
 
 	set_config('newest_user_colour', $row['user_colour'], true);
 
+	switch ($config['allow_name_chars'])
+	{
+		case '[\w]+':
+			set_config('allow_name_chars', '[a-z]+');
+		break;
+
+		case '[\w_\+\. \-\[\]]+':
+			set_config('allow_name_chars', '[-\]_+ [a-z]+');
+		break;
+	}
+
 	$no_updates = false;
 }
 
diff --git a/phpBB/language/en/acp/board.php b/phpBB/language/en/acp/board.php
index 02dabb9775..6270987935 100644
--- a/phpBB/language/en/acp/board.php
+++ b/phpBB/language/en/acp/board.php
@@ -204,6 +204,8 @@ $lang = array_merge($lang, array(
 	'REG_LIMIT_EXPLAIN'			=> 'Number of attempts users can make at the confirmation code before being locked out that session.',
 	'USERNAME_ALPHA_ONLY'		=> 'Alphanumeric only',
 	'USERNAME_ALPHA_SPACERS'	=> 'Alphanumeric and spacers',
+	'USERNAME_LETTER_NUM'		=> 'Any letter and number',
+	'USERNAME_LETTER_NUM_SPACERS'	=> 'Any letter, number, and spacer',
 	'USERNAME_CHARS'			=> 'Limit username chars',
 	'USERNAME_CHARS_ANY'		=> 'Any character',
 	'USERNAME_CHARS_EXPLAIN'	=> 'Restrict type of characters that may be used in usernames, spacers are; space, -, +, _, [ and ]',
diff --git a/phpBB/language/en/ucp.php b/phpBB/language/en/ucp.php
index 92d5225743..b336bca739 100644
--- a/phpBB/language/en/ucp.php
+++ b/phpBB/language/en/ucp.php
@@ -453,6 +453,8 @@ $lang = array_merge($lang, array(
 	'UPLOAD_AVATAR_URL_EXPLAIN'		=> 'Enter the URL of the location containing the image, it will be copied to this site.',
 	'USERNAME_ALPHA_ONLY_EXPLAIN'	=> 'Username must be between %1$d and %2$d chars long and use only alphanumeric characters',
 	'USERNAME_ALPHA_SPACERS_EXPLAIN'=> 'Username must be between %1$d and %2$d chars long and use alphanumeric, space or -+_[] characters.',
+	'USERNAME_LETTER_NUM_EXPLAIN'	=> 'Username must be between %1$d and %2$d chars long and use only letter or number characters',
+	'USERNAME_LETTER_NUM_SPACERS_EXPLAIN'=> 'Username must be between %1$d and %2$d chars long and use letter, number, space or -+_[] characters.',
 	'USERNAME_CHARS_ANY_EXPLAIN'	=> 'Length must be between %1$d and %2$d characters.',
 	'USERNAME_TAKEN_USERNAME'		=> 'The username you entered is already in use, please select an alternative.',
 	'USERNAME_DISALLOWED_USERNAME'	=> 'The username you entered has been banned.',