diff --git a/main-actions/src/main/scala/sbt/Package.scala b/main-actions/src/main/scala/sbt/Package.scala
index 7dcea5dac..82a9717c8 100644
--- a/main-actions/src/main/scala/sbt/Package.scala
+++ b/main-actions/src/main/scala/sbt/Package.scala
@@ -104,7 +104,7 @@ object Package {
     }
 
     val inputFiles = conf.sources.map(_._1).toSet
-    val inputs = conf.sources :+: lastModified(inputFiles) :+: manifest :+: HNil
+    val inputs = conf.sources.distinct :+: lastModified(inputFiles) :+: manifest :+: HNil
     cachedMakeJar(inputs)(() => exists(conf.jar))
     ()
   }
diff --git a/sbt/src/sbt-test/package/mappings/build.sbt b/sbt/src/sbt-test/package/mappings/build.sbt
index f135d3067..dc930b4ae 100644
--- a/sbt/src/sbt-test/package/mappings/build.sbt
+++ b/sbt/src/sbt-test/package/mappings/build.sbt
@@ -5,6 +5,7 @@ version := "0.2"
 mappings in (Compile, packageBin) ++= {
   val test = file("test")
   Seq(
+    test -> "test1",
     test -> "test1",
     test -> "test2"
   )