diff --git a/platform/indexing-impl/src/com/intellij/util/indexing/AdditionalIndexableFileSet.java b/platform/indexing-impl/src/com/intellij/util/indexing/AdditionalIndexableFileSet.java
index 0eb21e10dcd3..68f184724415 100644
--- a/platform/indexing-impl/src/com/intellij/util/indexing/AdditionalIndexableFileSet.java
+++ b/platform/indexing-impl/src/com/intellij/util/indexing/AdditionalIndexableFileSet.java
@@ -17,29 +17,33 @@ import org.jetbrains.annotations.Nullable;
 import java.util.Set;
 import java.util.function.Supplier;
 
-/**
- * @author peter
- */
 public class AdditionalIndexableFileSet implements IndexableFileSet {
   @Nullable
   private final Project myProject;
+  private final boolean myOnlyProjectPart;
   private final Supplier<IndexableSetContributor[]> myExtensions;
 
   private final CachedValue<AdditionalIndexableRoots> myAdditionalIndexableRoots;
 
   public AdditionalIndexableFileSet(@Nullable Project project, IndexableSetContributor @NotNull ... extensions) {
     myProject = project;
+    myOnlyProjectPart = false;
     myExtensions = () -> extensions;
     myAdditionalIndexableRoots = new CachedValueImpl<>(() -> new CachedValueProvider.Result<>(collectFilesAndDirectories(),
                                                                                               VirtualFileManager.VFS_STRUCTURE_MODIFICATIONS));
   }
 
-  public AdditionalIndexableFileSet(@Nullable Project project) {
+  public AdditionalIndexableFileSet(@Nullable Project project, boolean onlyProjectPart) {
     myProject = project;
     myExtensions = () -> IndexableSetContributor.EP_NAME.getExtensions();
     myAdditionalIndexableRoots = new CachedValueImpl<>(() -> new CachedValueProvider.Result<>(collectFilesAndDirectories(),
                                                                                               VirtualFileManager.VFS_STRUCTURE_MODIFICATIONS,
                                                                                               IndexableSetContributorModificationTracker.getInstance()));
+    myOnlyProjectPart = onlyProjectPart;
+  }
+
+  public AdditionalIndexableFileSet(@Nullable Project project) {
+    this(project, false);
   }
 
   public AdditionalIndexableFileSet() {
@@ -51,8 +55,10 @@ public class AdditionalIndexableFileSet implements IndexableFileSet {
     Set<VirtualFile> files = new THashSet<>();
     Set<VirtualFile> directories = new THashSet<>();
     for (IndexableSetContributor contributor : myExtensions.get()) {
-      for (VirtualFile root : IndexableSetContributor.getRootsToIndex(contributor)) {
-        (root.isDirectory() ? directories : files).add(root);
+      if (myProject == null || !myOnlyProjectPart) {
+        for (VirtualFile root : IndexableSetContributor.getRootsToIndex(contributor)) {
+          (root.isDirectory() ? directories : files).add(root);
+        }
       }
       if (myProject != null) {
         Set<VirtualFile> projectRoots = IndexableSetContributor.getProjectRootsToIndex(contributor, myProject);
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexProjectHandler.java b/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexProjectHandler.java
index f7edd62aff11..3692767f32d0 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexProjectHandler.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexProjectHandler.java
@@ -40,8 +40,6 @@ public final class FileBasedIndexProjectHandler implements IndexableFileSet {
   private final Project myProject;
   private final @NotNull ProjectFileIndex myProjectFileIndex;
 
-  private boolean isRemoved;
-
   private FileBasedIndexProjectHandler(@NotNull Project project) {
     myProject = project;
     myProjectFileIndex = ProjectFileIndex.getInstance(myProject);
@@ -76,23 +74,31 @@ public final class FileBasedIndexProjectHandler implements IndexableFileSet {
         DumbService.getInstance(project).queueTask(new UnindexedFilesUpdater(project, IndexInfrastructure.isIndexesInitializationSuspended()));
       }
 
-      FileBasedIndexProjectHandler handler = project.getService(FileBasedIndexProjectHandler.class);
-      fileBasedIndex.registerIndexableSet(handler, project);
+      for (Class<? extends IndexableFileSet> indexableSetClass : getProjectIndexableSetClasses()) {
+        IndexableFileSet set = project.getService(indexableSetClass);
+        fileBasedIndex.registerIndexableSet(set, project);
+      }
+
       // done mostly for tests. In real life this is no-op, because the set was removed on project closing
       Disposer.register(project, () -> removeProjectIndexableSet(project));
     }
 
     private static void removeProjectIndexableSet(@NotNull Project project) {
-      FileBasedIndexProjectHandler handler = project.getServiceIfCreated(FileBasedIndexProjectHandler.class);
-      if (handler != null && !handler.isRemoved) {
-        handler.isRemoved = true;
+      ProgressManager.getInstance().runProcessWithProgressSynchronously(() -> {
+        ReadAction.run(() -> {
+          for (Class<? extends IndexableFileSet> indexableSetClass : getProjectIndexableSetClasses()) {
+            IndexableFileSet set = project.getServiceIfCreated(indexableSetClass);
+            if (set != null) {
+              FileBasedIndex.getInstance().removeIndexableSet(set);
+            }
+          }
+        });
+      }, IndexingBundle.message("removing.indexable.set.project.handler"), false, project);
+    }
 
-        ProgressManager.getInstance().runProcessWithProgressSynchronously(() -> {
-          ReadAction.run(() -> {
-            FileBasedIndex.getInstance().removeIndexableSet(handler);
-          });
-        }, IndexingBundle.message("removing.indexable.set.project.handler"), false, project);
-      }
+    @SuppressWarnings("unchecked")
+    private static Class<? extends IndexableFileSet> @NotNull [] getProjectIndexableSetClasses() {
+      return new Class[]{FileBasedIndexProjectHandler.class, ProjectAdditionalIndexableFileSet.class};
     }
   }
 
@@ -199,4 +205,13 @@ public final class FileBasedIndexProjectHandler implements IndexableFileSet {
       }
     });
   }
+
+  // TODO automated project indexable file set management
+  @ApiStatus.Internal
+  @Service
+  public static final class ProjectAdditionalIndexableFileSet extends AdditionalIndexableFileSet {
+    public ProjectAdditionalIndexableFileSet(@NotNull Project project) {
+      super(project, true);
+    }
+  }
 }
diff --git a/platform/platform-tests/testSrc/com/intellij/openapi/roots/impl/indexing/IndexableFilesRegularTest.kt b/platform/platform-tests/testSrc/com/intellij/openapi/roots/impl/indexing/IndexableFilesRegularTest.kt
index 976d4c477857..3f9edb2e214c 100644
--- a/platform/platform-tests/testSrc/com/intellij/openapi/roots/impl/indexing/IndexableFilesRegularTest.kt
+++ b/platform/platform-tests/testSrc/com/intellij/openapi/roots/impl/indexing/IndexableFilesRegularTest.kt
@@ -1,15 +1,22 @@
 // Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.intellij.openapi.roots.impl.indexing
 
+import com.intellij.openapi.application.runWriteAction
 import com.intellij.openapi.project.Project
 import com.intellij.openapi.roots.AdditionalLibraryRootsProvider
 import com.intellij.openapi.roots.ModuleRootModificationUtil
 import com.intellij.openapi.roots.OrderRootType
 import com.intellij.openapi.roots.SyntheticLibrary
+import com.intellij.openapi.vfs.VfsUtil
 import com.intellij.openapi.vfs.VirtualFile
+import com.intellij.psi.impl.cache.CacheManager
+import com.intellij.psi.search.GlobalSearchScope
+import com.intellij.psi.search.UsageSearchContext
 import com.intellij.testFramework.RunsInEdt
+import com.intellij.testFramework.UsefulTestCase
 import com.intellij.util.indexing.IndexableSetContributor
 import org.junit.Test
+import kotlin.test.assertEquals
 
 @RunsInEdt
 class IndexableFilesRegularTest : IndexableFilesBaseTest() {
@@ -137,6 +144,17 @@ class IndexableFilesRegularTest : IndexableFilesBaseTest() {
     }
     maskIndexableSetContributors(contributor)
     assertIndexableFiles(additionalProjectRootJava.file, additionalRootJava.file)
+    assertIdIndexContainsWord(additionalRootJava.file, "AdditionalRoot")
+    assertIdIndexContainsWord(additionalProjectRootJava.file, "AdditionalProjectRoot")
+
+    // make some change
+    runWriteAction {
+      VfsUtil.saveText(additionalRootJava.file, "class Foo {}")
+      VfsUtil.saveText(additionalProjectRootJava.file, "class Foo {}")
+    }
+
+    assertIdIndexContainsWord(additionalRootJava.file, "Foo")
+    assertIdIndexContainsWord(additionalProjectRootJava.file, "Foo")
   }
 
   @Test
@@ -200,4 +218,16 @@ class IndexableFilesRegularTest : IndexableFilesBaseTest() {
     maskAdditionalLibraryRootsProviders(additionalLibraryRootsProvider)
     assertIndexableFiles(sourceFile.file, binaryFile.file, reIncludedSource.file, reIncludedBinary.file)
   }
+
+  private fun assertIdIndexContainsWord(file: VirtualFile, word: String) {
+    val fileScope = GlobalSearchScope.fileScope(project, file)
+    val cacheManager = CacheManager.getInstance(project)
+    val filesFromIndex = cacheManager.getVirtualFilesWithWord(word,
+                                                              UsageSearchContext.ANY,
+                                                              fileScope,
+                                                              true)
+
+    val fileFromIndex = UsefulTestCase.assertOneElement(filesFromIndex)
+    assertEquals(file, fileFromIndex)
+  }
 }
\ No newline at end of file