diff --git a/includes/diff/TextSlotDiffRenderer.php b/includes/diff/TextSlotDiffRenderer.php
index c254c08f189..22ca94ce912 100644
--- a/includes/diff/TextSlotDiffRenderer.php
+++ b/includes/diff/TextSlotDiffRenderer.php
@@ -92,14 +92,15 @@ class TextSlotDiffRenderer extends SlotDiffRenderer {
 	 * Convenience helper to use getTextDiff without an instance.
 	 * @param string $oldText
 	 * @param string $newText
+	 * @param array $options
 	 * @return string
 	 */
-	public static function diff( $oldText, $newText ) {
+	public static function diff( $oldText, $newText, $options = [] ) {
 		/** @var TextSlotDiffRenderer $slotDiffRenderer */
 		$slotDiffRenderer = MediaWikiServices::getInstance()
 			->getContentHandlerFactory()
 			->getContentHandler( CONTENT_MODEL_TEXT )
-			->getSlotDiffRenderer( RequestContext::getMain() );
+			->getSlotDiffRenderer( RequestContext::getMain(), $options );
 		'@phan-var TextSlotDiffRenderer $slotDiffRenderer';
 		return $slotDiffRenderer->getTextDiff( $oldText, $newText );
 	}
diff --git a/includes/languages/LanguageZh.php b/includes/languages/LanguageZh.php
index 4e23ca3934b..11aa6be4448 100644
--- a/includes/languages/LanguageZh.php
+++ b/includes/languages/LanguageZh.php
@@ -29,13 +29,22 @@
  */
 class LanguageZh extends LanguageZh_hans {
 	/**
-	 * this should give much better diff info
+	 * Add a formfeed character between each non-ASCII character, so that
+	 * "word-level" diffs will effectively operate on a character level. The FF
+	 * characters are stripped out by unsegmentForDiff().
+	 *
+	 * We use FF because it is the least used character that is matched by
+	 * PCRE's \s class.
+	 *
+	 * In the unlikely event that an FF character appears in the input, it will
+	 * be displayed in the diff as a replacement character.
 	 *
 	 * @param string $text
 	 * @return string
 	 */
 	public function segmentForDiff( $text ) {
-		return preg_replace( '/[\xc0-\xff][\x80-\xbf]*/', ' $0', $text );
+		$text = str_replace( "\x0c", "\u{FFFD}", $text );
+		return preg_replace( '/[\xc0-\xff][\x80-\xbf]*/', "\x0c$0", $text );
 	}
 
 	/**
@@ -43,7 +52,7 @@ class LanguageZh extends LanguageZh_hans {
 	 * @return string
 	 */
 	public function unsegmentForDiff( $text ) {
-		return preg_replace( '/ ([\xc0-\xff][\x80-\xbf]*)/', '$1', $text );
+		return str_replace( "\x0c", '', $text );
 	}
 
 	/**
diff --git a/tests/phpunit/includes/languages/LanguageZhTest.php b/tests/phpunit/includes/languages/LanguageZhTest.php
new file mode 100644
index 00000000000..815890d82d9
--- /dev/null
+++ b/tests/phpunit/includes/languages/LanguageZhTest.php
@@ -0,0 +1,20 @@
+<?php
+
+use MediaWiki\MainConfigNames;
+
+/**
+ * @covers LanguageZh
+ */
+class LanguageZhTest extends LanguageClassesTestCase {
+	public function testSegmentForDiff() {
+		$this->overrideConfigValue( MainConfigNames::DiffEngine, 'php' );
+		$lhs = '维基';
+		$rhs = '维基百科';
+		$diff = TextSlotDiffRenderer::diff( $lhs, $rhs, [ 'contentLanguage' => 'zh' ] );
+		// Check that only the second part is highlighted, and word segmentation markers are not present
+		$this->assertStringContainsString(
+			'<div>维基<ins class="diffchange diffchange-inline">百科</ins></div>',
+			$diff
+		);
+	}
+}