diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessor.php b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
index 48efd292d383f..e04f8cfd7d46d 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessor.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
@@ -913,7 +913,7 @@ public function test_set_inner_html_not_allowed( string $html, string $replaceme
 				break;
 			}
 		}
-		$this->assertFalse( $processor->set_inner_html( $replacement ) );
+		$this->assertFalse( $processor->set_inner_html( $replacement ), "Should have failed but produced: {$processor->get_updated_html()}" );
 		$this->assertSame( $html, $processor->get_updated_html() );
 	}