diff --git a/platform/platform-impl/src/com/intellij/openapi/fileTypes/impl/FileTypeManagerImpl.java b/platform/platform-impl/src/com/intellij/openapi/fileTypes/impl/FileTypeManagerImpl.java
index a65cc8cd1213..e9a1d6c5c480 100644
--- a/platform/platform-impl/src/com/intellij/openapi/fileTypes/impl/FileTypeManagerImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/fileTypes/impl/FileTypeManagerImpl.java
@@ -712,7 +712,6 @@ public class FileTypeManagerImpl extends FileTypeManagerEx implements Persistent
   }
 
   private void unregisterFileTypeWithoutNotification(@NotNull FileType fileType) {
-    CachedFileType.remove(fileType);
     myPatternsTable.removeAllAssociations(fileType);
     myInitialAssociations.removeAllAssociations(fileType);
     mySchemeManager.removeScheme(fileType);
@@ -809,6 +808,7 @@ public class FileTypeManagerImpl extends FileTypeManagerEx implements Persistent
 
   private void fireFileTypesChanged(@Nullable FileType addedFileType, @Nullable FileType removedFileType) {
     myDetectionService.clearCaches();
+    CachedFileType.clearCache();
     ApplicationManager.getApplication().getMessageBus().syncPublisher(TOPIC).fileTypesChanged(new FileTypeEvent(this, addedFileType, removedFileType));
   }
 
diff --git a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/CachedFileType.java b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/CachedFileType.java
index 141da3f24e8e..1779d1ffb672 100644
--- a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/CachedFileType.java
+++ b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/CachedFileType.java
@@ -1,6 +1,7 @@
 // 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.vfs.newvfs.impl;
 
+import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.fileTypes.FileType;
 import com.intellij.psi.util.PsiModificationTracker;
 import org.jetbrains.annotations.ApiStatus;
@@ -25,10 +26,12 @@ public final class CachedFileType {
   }
 
   static CachedFileType forType(@NotNull FileType fileType) {
+    ApplicationManager.getApplication().assertReadAccessAllowed();
     return ourInterner.computeIfAbsent(fileType, CachedFileType::new);
   }
 
   public static void clearCache() {
+    ApplicationManager.getApplication().assertWriteAccessAllowed();
     ourInterner.forEach((type, cachedType) -> {
       // clear references to file types to aid plugin unloading
       cachedType.fileType = null;
@@ -36,13 +39,6 @@ public final class CachedFileType {
     ourInterner.clear();
   }
 
-  public static void remove(@NotNull FileType type) {
-    CachedFileType cached = ourInterner.remove(type);
-    if (cached != null) {
-      cached.fileType = null;
-    }
-  }
-
   static final class PsiListener implements PsiModificationTracker.Listener {
     @Override
     public void modificationCountChanged() {
diff --git a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/VirtualFileSystemEntry.java b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/VirtualFileSystemEntry.java
index ba2b39974433..200ce673a3ae 100644
--- a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/VirtualFileSystemEntry.java
+++ b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/VirtualFileSystemEntry.java
@@ -485,7 +485,9 @@ public abstract class VirtualFileSystemEntry extends NewVirtualFile {
     FileType type = cache == null ? null : cache.getUpToDateOrNull();
     if (type == null) {
       type = super.getFileType();
-      myFileType = CachedFileType.forType(type);
+      if (ApplicationManager.getApplication().isReadAccessAllowed()) {
+        myFileType = CachedFileType.forType(type);
+      }
     }
     return type;
   }
diff --git a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/FSRecords.java b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/FSRecords.java
index 248304e47469..deaa9fe44974 100644
--- a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/FSRecords.java
+++ b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/FSRecords.java
@@ -1,8 +1,6 @@
 // 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.vfs.newvfs.persistent;
 
-import com.google.common.hash.HashFunction;
-import com.google.common.hash.Hashing;
 import com.intellij.ide.IdeBundle;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.application.ApplicationNamesInfo;
@@ -20,7 +18,6 @@ import com.intellij.openapi.vfs.impl.local.LocalFileSystemImpl;
 import com.intellij.openapi.vfs.newvfs.ChildInfoImpl;
 import com.intellij.openapi.vfs.newvfs.FileAttribute;
 import com.intellij.openapi.vfs.newvfs.events.ChildInfo;
-import com.intellij.openapi.vfs.newvfs.impl.CachedFileType;
 import com.intellij.openapi.vfs.newvfs.impl.FileNameCache;
 import com.intellij.openapi.vfs.newvfs.impl.VirtualDirectoryImpl;
 import com.intellij.openapi.vfs.newvfs.impl.VirtualFileSystemEntry;
@@ -1186,7 +1183,6 @@ public final class FSRecords {
 
   private static void incModCount(int id) {
     incLocalModCount();
-    CachedFileType.clearCache();
 
     final int count = doGetModCount() + 1;
     getRecords().putInt(HEADER_GLOBAL_MOD_COUNT_OFFSET, count);
diff --git a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/PersistentFSImpl.java b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/PersistentFSImpl.java
index e7ce048b625b..ea269b59b185 100644
--- a/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/PersistentFSImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/persistent/PersistentFSImpl.java
@@ -1044,6 +1044,7 @@ public final class PersistentFSImpl extends PersistentFS implements Disposable {
   }
 
   private static void fireAfterEvents(@NotNull BulkFileListener publisher, @NotNull List<? extends VFileEvent> toSend) {
+    CachedFileType.clearCache();
     ((BulkFileListener)VirtualFilePointerManager.getInstance()).after(toSend);
     publisher.after(toSend);
   }
diff --git a/platform/platform-tests/testSrc/com/intellij/openapi/fileTypes/impl/FileTypesTest.java b/platform/platform-tests/testSrc/com/intellij/openapi/fileTypes/impl/FileTypesTest.java
index 4cc577e58578..a70cce34cb10 100644
--- a/platform/platform-tests/testSrc/com/intellij/openapi/fileTypes/impl/FileTypesTest.java
+++ b/platform/platform-tests/testSrc/com/intellij/openapi/fileTypes/impl/FileTypesTest.java
@@ -930,7 +930,7 @@ public class FileTypesTest extends HeavyPlatformTestCase {
     bean.fileNames = ".prettierrc";
     bean.implementationClass = MyTestFileType.class.getName();
     Disposable disposable = registerFileType(bean);
-    CachedFileType.clearCache();   // normally this is done by PsiModificationTracker.Listener but it's not fired in this test
+    clearFileTypeCache();
 
     assertEquals(MyTestFileType.NAME, FileTypeManager.getInstance().getFileTypeByFileName(".prettierrc").getName());
     assertEquals(MyTestFileType.NAME, vFile.getFileType().getName());
@@ -939,6 +939,10 @@ public class FileTypesTest extends HeavyPlatformTestCase {
     assertNull(FileTypeManager.getInstance().findFileTypeByName(MyTestFileType.NAME));
   }
 
+  private static void clearFileTypeCache() {
+    WriteAction.run(() -> CachedFileType.clearCache());   // normally this is done by PsiModificationTracker.Listener but it's not fired in this test
+  }
+
   public void testRegisterAdditionalExtensionForExistingFileType() throws IOException {
     File tempFile = createTempFile(".prettierrc", "This is a text file");
     VirtualFile vFile = getVirtualFile(tempFile);
@@ -948,7 +952,7 @@ public class FileTypesTest extends HeavyPlatformTestCase {
     bean.name = "XML";
     bean.fileNames = ".prettierrc";
     Disposable disposable = registerFileType(bean);
-    CachedFileType.clearCache();   // normally this is done by PsiModificationTracker.Listener but it's not fired in this test
+    clearFileTypeCache();
 
     assertEquals("XML", FileTypeManager.getInstance().getFileTypeByFileName(".prettierrc").getName());
     assertEquals("XML", vFile.getFileType().getName());