diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index bbd3504b3..0052042e6 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -47,7 +47,7 @@ import sbt.util.InterfaceUtil.{ f1, o2m }
 import sbt.internal.util.Types._
 
 import sbt.internal.io.WatchState
-import sbt.io.{ AllPassFilter, FileFilter, GlobFilter, HiddenFileFilter, IO, NameFilter, NothingFilter, Path, PathFinder }
+import sbt.io.{ AllPassFilter, FileFilter, GlobFilter, HiddenFileFilter, IO, NameFilter, NothingFilter, Path, PathFinder, SimpleFileFilter }
 
 import Path._
 import Keys._
@@ -105,7 +105,7 @@ object Defaults extends BuildCommon {
       artifactClassifier in packageSrc :== Some(SourceClassifier),
       artifactClassifier in packageDoc :== Some(DocClassifier),
       includeFilter :== NothingFilter,
-      includeFilter in unmanagedSources :== "*.java" | "*.scala",
+      includeFilter in unmanagedSources :== ("*.java" | "*.scala") && new SimpleFileFilter(_.isFile),
       includeFilter in unmanagedJars :== "*.jar" | "*.so" | "*.dll" | "*.jnilib" | "*.zip",
       includeFilter in unmanagedResources :== AllPassFilter
     )
diff --git a/sbt/src/sbt-test/tests/source-directory-name/src/main/scala/ch.epfl.scala/Client.scala b/sbt/src/sbt-test/tests/source-directory-name/src/main/scala/ch.epfl.scala/Client.scala
new file mode 100644
index 000000000..b08d24b3b
--- /dev/null
+++ b/sbt/src/sbt-test/tests/source-directory-name/src/main/scala/ch.epfl.scala/Client.scala
@@ -0,0 +1,4 @@
+package ch.epfl.scala
+
+// https://github.com/sbt/sbt/issues/2552
+class Client
diff --git a/sbt/src/sbt-test/tests/source-directory-name/test b/sbt/src/sbt-test/tests/source-directory-name/test
new file mode 100644
index 000000000..23b3323ba
--- /dev/null
+++ b/sbt/src/sbt-test/tests/source-directory-name/test
@@ -0,0 +1,2 @@
+> compile
+$ exists target/scala-2.11/classes/ch/epfl/scala/Client.class