diff --git a/main/src/main/scala/sbt/internal/server/BuildServerProtocol.scala b/main/src/main/scala/sbt/internal/server/BuildServerProtocol.scala
index 657653345..b5006aabb 100644
--- a/main/src/main/scala/sbt/internal/server/BuildServerProtocol.scala
+++ b/main/src/main/scala/sbt/internal/server/BuildServerProtocol.scala
@@ -116,21 +116,18 @@ object BuildServerProtocol {
             val base = loadedBuildUnit.localBase
             val sbtFiles = configurationSources(base)
             val pluginData = loadedBuildUnit.unit.plugins.pluginData
-            val all = Vector.newBuilder[SourceItem]
-            def add(fs: Seq[File], sourceItemKind: Int, generated: Boolean): Unit = {
-              fs.foreach(f => all += (SourceItem(f.toURI, sourceItemKind, generated = generated)))
-            }
-            all += (SourceItem(
-              loadedBuildUnit.unit.plugins.base.toURI,
-              SourceItemKind.Directory,
-              generated = false
-            ))
-            add(pluginData.unmanagedSourceDirectories, SourceItemKind.Directory, generated = false)
-            add(pluginData.unmanagedSources, SourceItemKind.File, generated = false)
-            add(pluginData.managedSourceDirectories, SourceItemKind.Directory, generated = true)
-            add(pluginData.managedSources, SourceItemKind.File, generated = true)
-            add(sbtFiles, SourceItemKind.File, generated = false)
-            Value(SourcesItem(id, all.result()))
+            val dirs = pluginData.unmanagedSourceDirectories
+            val sourceFiles = getStandaloneSourceFiles(pluginData.unmanagedSources, dirs)
+            val managedDirs = pluginData.managedSourceDirectories
+            val managedSourceFiles =
+              getStandaloneSourceFiles(pluginData.managedSources, managedDirs)
+            val items =
+              dirs.map(toSourceItem(SourceItemKind.Directory, generated = false)) ++
+                sourceFiles.map(toSourceItem(SourceItemKind.File, generated = false)) ++
+                managedDirs.map(toSourceItem(SourceItemKind.Directory, generated = true)) ++
+                managedSourceFiles.map(toSourceItem(SourceItemKind.File, generated = true)) ++
+                sbtFiles.map(toSourceItem(SourceItemKind.File, generated = false))
+            Value(SourcesItem(id, items.toVector))
         }
         val successfulItems = anyOrThrow(items ++ buildItems)
         val result = SourcesResult(successfulItems.toVector)
@@ -280,10 +277,6 @@ object BuildServerProtocol {
       val sourceFiles = getStandaloneSourceFiles(unmanagedSources.value, dirs)
       val managedDirs = managedSourceDirectories.value
       val managedSourceFiles = getStandaloneSourceFiles(managedSources.value, managedDirs)
-
-      def toSourceItem(itemKind: Int, generated: Boolean)(file: File): SourceItem =
-        SourceItem(file.toURI, itemKind, generated)
-
       val items = dirs.map(toSourceItem(SourceItemKind.Directory, generated = false)) ++
         sourceFiles.map(toSourceItem(SourceItemKind.File, generated = false)) ++
         managedDirs.map(toSourceItem(SourceItemKind.Directory, generated = true)) ++
@@ -469,6 +462,9 @@ object BuildServerProtocol {
     }
   }
 
+  private def toSourceItem(itemKind: Int, generated: Boolean)(file: File): SourceItem =
+    SourceItem(file.toURI, itemKind, generated)
+
   private def checkMetalsCompatibility(
       semanticdbEnabled: Boolean,
       semanticdbVersion: String,
diff --git a/server-test/src/test/scala/testpkg/BuildServerTest.scala b/server-test/src/test/scala/testpkg/BuildServerTest.scala
index f5340e131..5aa231752 100644
--- a/server-test/src/test/scala/testpkg/BuildServerTest.scala
+++ b/server-test/src/test/scala/testpkg/BuildServerTest.scala
@@ -79,14 +79,12 @@ object BuildServerTest extends AbstractServerTest {
     val sources = s.items.head.sources.map(_.uri).sorted
     val expectedSources = Vector(
       "build.sbt",
-      "project/",
       "project/A.scala",
       "project/src/main/java",
       "project/src/main/scala-2",
       "project/src/main/scala-2.12",
       "project/src/main/scala-sbt-1.0",
       "project/src/main/scala/",
-      "project/src/main/scala/B.scala",
       "project/target/scala-2.12/sbt-1.0/src_managed/main"
     ).map(rel => new File(svr.baseDirectory.getAbsoluteFile, rel).toURI).sorted
     assert(sources == expectedSources)