diff --git a/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java b/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java
index 32673635d193..bfdbec406a8a 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java
@@ -1938,13 +1938,15 @@ public class FileBasedIndexImpl extends FileBasedIndex implements BaseComponent,
           !PowerSaveMode.isEnabled()) {
         myScheduledVfsEventsWorkers.incrementAndGet();
         myVfsEventsExecutor.submit(this::processFilesInReadActionWithYieldingToWriteAction);
-        
-        for(Project project:ProjectManager.getInstance().getOpenProjects()) {
-          DumbServiceImpl dumbService = DumbServiceImpl.getInstance(project);
-          DumbModeTask task = FileBasedIndexProjectHandler.createChangedFilesIndexingTask(project);
 
-          if (task != null) {
-            dumbService.queueTask(task);
+        if (!ApplicationManager.getApplication().isHeadlessEnvironment()) {  // avoid synchronous ensureUpToDate to prevent deadlock
+          for(Project project:ProjectManager.getInstance().getOpenProjects()) {
+            DumbServiceImpl dumbService = DumbServiceImpl.getInstance(project);
+            DumbModeTask task = FileBasedIndexProjectHandler.createChangedFilesIndexingTask(project);
+  
+            if (task != null) {
+              dumbService.queueTask(task);
+            }
           }
         }
       }