diff --git a/platform/lang-impl/src/com/intellij/util/indexing/ProjectFileBasedIndexStartupActivity.java b/platform/lang-impl/src/com/intellij/util/indexing/ProjectFileBasedIndexStartupActivity.java
index 17217cf28f4a..7aeb960e4b65 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/ProjectFileBasedIndexStartupActivity.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/ProjectFileBasedIndexStartupActivity.java
@@ -46,11 +46,10 @@ final class ProjectFileBasedIndexStartupActivity implements StartupActivity.Requ
       if (project.isDisposed()) return false;
       // done mostly for tests. In real life this is no-op, because the set was removed on project closing
       Disposer.register(project, () -> onProjectClosing(project));
+      myOpenProjects.add(project);
 
       fileBasedIndex.registerProjectFileSets(project);
       fileBasedIndex.getIndexableFilesFilterHolder().onProjectOpened(project);
-
-      myOpenProjects.add(project);
       return true;
     });