diff --git a/project/SparkBuild.scala b/project/SparkBuild.scala
index 6b8740d9f21a1..21163760e6277 100644
--- a/project/SparkBuild.scala
+++ b/project/SparkBuild.scala
@@ -195,6 +195,7 @@ object SparkBuild extends Build {
     concurrentRestrictions in Global += Tags.limit(Tags.Test, 1),
 
     resolvers ++= Seq(
+      // HTTPS is unavailable for Maven Central
       "Maven Repository"     at "http://repo.maven.apache.org/maven2",
       "Apache Repository"    at "https://repository.apache.org/content/repositories/releases",
       "JBoss Repository"     at "https://repository.jboss.org/nexus/content/repositories/releases/",