diff --git a/spring-cloud-build-tools/src/main/resources/checkstyle.xml b/spring-cloud-build-tools/src/main/resources/checkstyle.xml
index 1ab895ff..19e99953 100644
--- a/spring-cloud-build-tools/src/main/resources/checkstyle.xml
+++ b/spring-cloud-build-tools/src/main/resources/checkstyle.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <!DOCTYPE module PUBLIC
 		"-//Puppy Crawl//DTD Check Configuration 1.3//EN"
-		"http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+		"https://www.puppycrawl.com/dtds/configuration_1_3.dtd">
 <module name="Checker">
 	<module name="TreeWalker">
 		<!-- this. in front of fields -->