diff --git a/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/FileDocumentManagerImpl.java b/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/FileDocumentManagerImpl.java
index 8d74839e52ba..af229d1abb18 100644
--- a/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/FileDocumentManagerImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/fileEditor/impl/FileDocumentManagerImpl.java
@@ -748,7 +748,8 @@ public class FileDocumentManagerImpl extends FileDocumentManager implements Virt
   @Override
   public void beforeContentsChange(@NotNull VirtualFileEvent event) {
     VirtualFile virtualFile = event.getFile();
-    if (virtualFile.getFileType() == UnknownFileType.INSTANCE && virtualFile.getLength() == 0) {
+    // check file type in second order to avoid content detection running
+    if (virtualFile.getLength() == 0 && virtualFile.getFileType() == UnknownFileType.INSTANCE) {
       virtualFile.putUserData(MUST_RECOMPUTE_FILE_TYPE, Boolean.TRUE);
     }
   }