diff --git a/main/Defaults.scala b/main/Defaults.scala
index 535ddf317..6e4b477b2 100755
--- a/main/Defaults.scala
+++ b/main/Defaults.scala
@@ -70,6 +70,7 @@ object Defaults extends BuildCommon
 		logBuffered :== false,
 		connectInput :== false,
 		cancelable :== false,
+		sourcesInBase :== true,
 		autoScalaLibrary :== true,
 		onLoad <<= onLoad ?? idFun[State],
 		onUnload <<= (onUnload ?? idFun[State]),
@@ -182,8 +183,8 @@ object Defaults extends BuildCommon
 		docDirectory <<= (crossTarget, configuration) { (outDir, conf) => outDir / (prefix(conf.name) + "api") }
 	)
 	def addBaseSources = Seq(
-		unmanagedSources <<= (unmanagedSources, baseDirectory, includeFilter in unmanagedSources, excludeFilter in unmanagedSources) map {
-			(srcs,b,f,excl) => (srcs +++ b * (f -- excl)).get
+		unmanagedSources <<= (unmanagedSources, baseDirectory, includeFilter in unmanagedSources, excludeFilter in unmanagedSources, sourcesInBase) map {
+			(srcs,b,f,excl,enable) => if(enable) (srcs +++ b * (f -- excl)).get else srcs
 		}
 	)
 
diff --git a/main/Keys.scala b/main/Keys.scala
index 07ee6e2bb..8979dd75d 100644
--- a/main/Keys.scala
+++ b/main/Keys.scala
@@ -88,6 +88,7 @@ object Keys
 	val managedSourceDirectories = SettingKey[Seq[File]]("managed-source-directories", "Managed source directories, which contain sources generated by the build.", BSetting)
 	val managedSources = TaskKey[Seq[File]]("managed-sources", "Sources generated by the build.", BTask)
 	val sources = TaskKey[Seq[File]]("sources", "All sources, both managed and unmanaged.", BTask)
+	val sourcesInBase = SettingKey[Boolean]("sources-in-base", "If true, sources from the project's base directory are included as main sources.")
 
 		// Filters
 	val includeFilter = SettingKey[FileFilter]("include-filter", "Filter for including sources and resources files from default directories.", CSetting)
diff --git a/sbt/src/sbt-test/project/base-sources/A.scala b/sbt/src/sbt-test/project/base-sources/A.scala
new file mode 100644
index 000000000..9977a2836
--- /dev/null
+++ b/sbt/src/sbt-test/project/base-sources/A.scala
@@ -0,0 +1 @@
+invalid
diff --git a/sbt/src/sbt-test/project/base-sources/test b/sbt/src/sbt-test/project/base-sources/test
new file mode 100644
index 000000000..7a7f2606b
--- /dev/null
+++ b/sbt/src/sbt-test/project/base-sources/test
@@ -0,0 +1,3 @@
+-> compile
+> set sourcesInBase := false
+> compile