diff --git a/gradle/jdiff.gradle b/gradle/jdiff.gradle
index cc07e3f71b..da454e62ab 100644
--- a/gradle/jdiff.gradle
+++ b/gradle/jdiff.gradle
@@ -43,6 +43,7 @@ task jdiff {
 		ant.mkdir(dir: outputDir)
 		ant.jdiff(
 				destdir: outputDir,
+				source: "1.8",
 				verbose: "off",
 				stats: "on",
 				docchanges: "off") {