diff --git a/tests/phpunit/tests/customize/custom-css-setting.php b/tests/phpunit/tests/customize/custom-css-setting.php
index 898ca610c0..d1d2a18124 100644
--- a/tests/phpunit/tests/customize/custom-css-setting.php
+++ b/tests/phpunit/tests/customize/custom-css-setting.php
@@ -125,7 +125,7 @@ class Test_WP_Customize_Custom_CSS_Setting extends WP_UnitTestCase {
 		$this->wp_customize->set_post_value( $this->setting->id, $updated_css );
 		$saved = $this->setting->save();
 
-		$this->assertNotFalse( $saved );
+		$this->assertTrue( false !== $saved );
 		$this->assertEquals( $updated_css, $this->setting->value() );
 		$this->assertEquals( $updated_css, wp_get_custom_css( $this->setting->stylesheet ) );