maven-javadoc-plugin -> <source>8</source>
diff --git a/pom.xml b/pom.xml
index fa5a219..55a1de2 100644
--- a/pom.xml
+++ b/pom.xml
@@ -253,6 +253,7 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>
         <configuration>
+          <source>8</source>
           <additionalparam>-Xdoclint:none</additionalparam>
           <stylesheet>java</stylesheet>
           <bottom>&lt;small&gt;Copyright &amp;copy; 2003-2016, The Apache Software Foundation. All Rights Reserved. Generated ${maven.build.timestamp}&lt;/small&gt;</bottom>