diff --git a/includes/diff/DifferenceEngine.php b/includes/diff/DifferenceEngine.php
index 0e7019f2e88..3c5ed653864 100644
--- a/includes/diff/DifferenceEngine.php
+++ b/includes/diff/DifferenceEngine.php
@@ -776,9 +776,9 @@ class DifferenceEngine extends ContextSource {
 
 		# Allow extensions to define their own revision tools
 		$this->hookRunner->onDiffTools(
-			$this->mOldRevisionRecord,
-			$revisionTools,
 			$this->mNewRevisionRecord,
+			$revisionTools,
+			$this->mOldRevisionRecord,
 			$user
 		);