diff --git a/src/server/features/bufferSyncSupport.ts b/src/server/features/bufferSyncSupport.ts
index 789104e..326c965 100644
--- a/src/server/features/bufferSyncSupport.ts
+++ b/src/server/features/bufferSyncSupport.ts
@@ -280,6 +280,10 @@ export default class BufferSyncSupport {
     this.triggerDiagnostics()
   }
 
+  public has(uri: string): boolean {
+    return this.uris.has(uri)
+  }
+
   private triggerDiagnostics(delay = 200): void {
     this.diagnosticDelayer.trigger(() => {
       this.sendPendingDiagnostics()
diff --git a/src/server/features/fileConfigurationManager.ts b/src/server/features/fileConfigurationManager.ts
index 5b7129d..f8e24ba 100644
--- a/src/server/features/fileConfigurationManager.ts
+++ b/src/server/features/fileConfigurationManager.ts
@@ -65,6 +65,7 @@ export default class FileConfigurationManager {
 
   public async ensureConfigurationForDocument(document: TextDocument): Promise<void> {
     let opts = await workspace.getFormatOptions(document.uri)
+    if (!this.client.bufferSyncSupport.has(document.uri)) return
     return this.ensureConfigurationOptions(document.languageId, opts.insertSpaces, opts.tabSize)
   }