diff --git a/phpBB/includes/error_collector.php b/phpBB/includes/error_collector.php
index 534df27ece..040be4dd13 100644
--- a/phpBB/includes/error_collector.php
+++ b/phpBB/includes/error_collector.php
@@ -42,8 +42,6 @@ class phpbb_error_collector
 
 	function format_errors()
 	{
-		$phpbb_root_path = phpbb_realpath(dirname(__FILE__) . '/../');
-
 		$text = '';
 		foreach ($this->errors as $error)
 		{
@@ -55,7 +53,7 @@ class phpbb_error_collector
 			list($errno, $msg_text, $errfile, $errline) = $error;
 
 			// Prevent leakage of local path to phpBB install
-			$errfile = str_replace(array($phpbb_root_path, '\\'), array('', '/'), $errfile);
+			$errfile = phpbb_filter_errfile($errfile);
 
 			$text .= "Errno $errno: $msg_text at $errfile line $errline";
 		}
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 628f8ee123..4c1bfb4360 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -3816,9 +3816,8 @@ function msg_handler($errno, $msg_text, $errfile, $errline)
 
 			if (strpos($errfile, 'cache') === false && strpos($errfile, 'template.') === false)
 			{
-				// remove complete path to installation, with the risk of changing backslashes meant to be there
-				$errfile = str_replace(array(phpbb_realpath($phpbb_root_path), '\\'), array('', '/'), $errfile);
-				$msg_text = str_replace(array(phpbb_realpath($phpbb_root_path), '\\'), array('', '/'), $msg_text);
+				$errfile = phpbb_filter_errfile($errfile);
+				$msg_text = phpbb_filter_errfile($msg_text);
 				$error_name = ($errno === E_WARNING) ? 'PHP Warning' : 'PHP Notice';
 				echo '<b>[phpBB Debug] ' . $error_name . '</b>: in file <b>' . $errfile . '</b> on line <b>' . $errline . '</b>: <b>' . $msg_text . '</b><br />' . "\n";
 
@@ -3996,6 +3995,27 @@ function msg_handler($errno, $msg_text, $errfile, $errline)
 	return false;
 }
 
+/**
+* Removes absolute path to phpBB root directory from error messages
+* and converts backslashes to forward slashes.
+*
+* @param string $errfile	Absolute file path
+*							(e.g. /var/www/phpbb3/phpBB/includes/functions.php)
+* @return string			Relative file path
+*							(e.g. /includes/functions.php)
+*/
+function phpbb_filter_errfile($errfile)
+{
+	static $root_path;
+
+	if (empty($root_path))
+	{
+		$root_path = phpbb_realpath(dirname(__FILE__) . '/../');
+	}
+
+	return str_replace(array($root_path, '\\'), array('', '/'), $errfile);
+}
+
 /**
 * Queries the session table to get information about online guests
 * @param int $item_id Limits the search to the item with this id