diff --git a/src/Cite.php b/src/Cite.php
index f55ee300b..0613329ae 100644
--- a/src/Cite.php
+++ b/src/Cite.php
@@ -299,7 +299,7 @@ class Cite {
 		// Tag every page where Book Referencing has been used, whether or not the ref tag is valid.
 		// This code and the page property will be removed once the feature is stable.  See T237531.
 		if ( array_key_exists( self::BOOK_REF_ATTRIBUTE, $argv ) ) {
-			$parser->getOutput()->setPageProperty( self::BOOK_REF_PROPERTY, true );
+			$parser->getOutput()->setPageProperty( self::BOOK_REF_PROPERTY, '' );
 		}
 
 		$status = $this->parseArguments(
diff --git a/tests/phpunit/unit/CiteUnitTest.php b/tests/phpunit/unit/CiteUnitTest.php
index a4c121c99..31e21ffa5 100644
--- a/tests/phpunit/unit/CiteUnitTest.php
+++ b/tests/phpunit/unit/CiteUnitTest.php
@@ -658,7 +658,7 @@ class CiteUnitTest extends \MediaWikiUnitTestCase {
 		// This will be our most important assertion.
 		$mockOutput->expects( $this->once() )
 			->method( 'setPageProperty' )
-			->with( Cite::BOOK_REF_PROPERTY, true );
+			->with( Cite::BOOK_REF_PROPERTY, '' );
 
 		$mockParser = $this->createMock( Parser::class );
 		$mockParser->method( 'getOutput' )->willReturn( $mockOutput );