diff --git a/tools/build/conf/src/main/resources/onos/checkstyle.xml b/tools/build/conf/src/main/resources/onos/checkstyle.xml
index 6387d2b..1d365a9 100644
--- a/tools/build/conf/src/main/resources/onos/checkstyle.xml
+++ b/tools/build/conf/src/main/resources/onos/checkstyle.xml
@@ -108,6 +108,7 @@
 
     <module name="RegexpHeader">
         <property name="headerFile" value="tools/build/conf/src/main/resources/onos/onos-java.header"/>
+        <property name="fileExtensions" value="java"/>
     </module>