diff --git a/io/src/main/scala/sbt/io/PathMapper.scala b/io/src/main/scala/sbt/io/PathMapper.scala
index 78c51c20..25bbd964 100644
--- a/io/src/main/scala/sbt/io/PathMapper.scala
+++ b/io/src/main/scala/sbt/io/PathMapper.scala
@@ -112,12 +112,10 @@ abstract class Mapper {
    * Selects descendants of `base` directory matching `filter` and maps them to a path relative to `base`.
    * `base` itself is not included.
    */
-  def selectSubpaths(base: File, filter: FileFilter): Traversable[(File, String)] = {
-    val path = base.toPath
+  def selectSubpaths(base: File, filter: FileFilter): Traversable[(File, String)] =
     PathFinder(base).globRecursive(filter).get().collect {
-      case f if f != path => f -> path.relativize(f.toPath).toString
+      case f if f != base => f -> base.toPath.relativize(f.toPath).toString
     }
-  }
 
   /**
    * return a Seq of mappings which effect is to add a whole directory in the generated package
diff --git a/io/src/test/scala/sbt/io/PathMapperSpec.scala b/io/src/test/scala/sbt/io/PathMapperSpec.scala
index 8b282572..ed533ef3 100644
--- a/io/src/test/scala/sbt/io/PathMapperSpec.scala
+++ b/io/src/test/scala/sbt/io/PathMapperSpec.scala
@@ -128,6 +128,13 @@ class PathMapperSpec extends fixture.FlatSpec with Matchers {
     mappings should be(empty)
   }
 
+  it should "not include the base directory" in { tempDirectory =>
+    val file = Files.createFile(tempDirectory.resolve("file"))
+    val paths = Path.allSubpaths(tempDirectory.toFile).toVector.map(_._1.toPath).toSet
+    assert(paths.contains(file))
+    assert(!paths.contains(tempDirectory))
+  }
+
   override protected def withFixture(test: OneArgTest): Outcome = {
     val tmpDir = Files.createTempDirectory("path-mappings")
     try {