diff --git a/wp-includes/Text/Diff.php b/wp-includes/Text/Diff.php
index f8a974c1c..06d1c6c76 100644
--- a/wp-includes/Text/Diff.php
+++ b/wp-includes/Text/Diff.php
@@ -49,7 +49,8 @@ class Text_Diff {
             $engine = basename($engine);
         }
 
-        require_once 'Text/Diff/Engine/' . $engine . '.php';
+        // WP #7391
+        require_once dirname(__FILE__).'/Diff/Engine/' . $engine . '.php';
         $class = 'Text_Diff_Engine_' . $engine;
         $diff_engine = new $class();
 
diff --git a/wp-includes/Text/Diff/Renderer/inline.php b/wp-includes/Text/Diff/Renderer/inline.php
index b547ff236..1493eaa04 100644
--- a/wp-includes/Text/Diff/Renderer/inline.php
+++ b/wp-includes/Text/Diff/Renderer/inline.php
@@ -14,7 +14,9 @@
  */
 
 /** Text_Diff_Renderer */
-require_once 'Text/Diff/Renderer.php';
+
+// WP #7391
+require_once dirname(dirname(__FILE__)) . '/Renderer.php';
 
 /**
  * "Inline" diff renderer.
diff --git a/wp-includes/pluggable.php b/wp-includes/pluggable.php
index b9409669a..34d5b426e 100644
--- a/wp-includes/pluggable.php
+++ b/wp-includes/pluggable.php
@@ -1530,10 +1530,6 @@ function wp_text_diff( $left_string, $right_string, $args = null ) {
 	$defaults = array( 'title' => '', 'title_left' => '', 'title_right' => '' );
 	$args = wp_parse_args( $args, $defaults );
 
-	// PEAR Text_Diff is lame; it includes things from include_path rather than it's own path.
-	// Not sure of the ramifications of disttributing modified code.
-	ini_set('include_path', '.' . PATH_SEPARATOR . ABSPATH . WPINC );
-
 	if ( !class_exists( 'WP_Text_Diff_Renderer_Table' ) )
 		require( ABSPATH . WPINC . '/wp-diff.php' );
 
@@ -1552,8 +1548,6 @@ function wp_text_diff( $left_string, $right_string, $args = null ) {
 	$renderer  = new WP_Text_Diff_Renderer_Table();
 	$diff = $renderer->render($text_diff);
 
-	ini_restore('include_path');
-
 	if ( !$diff )
 		return '';
 
diff --git a/wp-includes/wp-diff.php b/wp-includes/wp-diff.php
index 77f325812..e43903d80 100644
--- a/wp-includes/wp-diff.php
+++ b/wp-includes/wp-diff.php
@@ -1,9 +1,9 @@
 <?php
 
 if ( !class_exists( 'Text_Diff' ) ) {
-	require( 'Text/Diff.php' );
-	require( 'Text/Diff/Renderer.php' );
-	require( 'Text/Diff/Renderer/inline.php' );
+	require( dirname(__FILE__).'/Text/Diff.php' );
+	require( dirname(__FILE__).'/Text/Diff/Renderer.php' );
+	require( dirname(__FILE__).'/Text/Diff/Renderer/inline.php' );
 }