Index: clangd/ClangdLSPServer.h
===================================================================
--- clangd/ClangdLSPServer.h
+++ clangd/ClangdLSPServer.h
@@ -113,6 +113,10 @@
   void reparseOpenedFiles();
   void applyConfiguration(const ConfigurationSettings &Settings);
 
+  /// Sends a "publishDiagnostics" notification to the LSP client.
+  void publishDiagnostics(const URIForFile &File,
+                          std::vector<clangd::Diagnostic> Diagnostics);
+
   /// Used to indicate that the 'shutdown' request was received from the
   /// Language Server client.
   bool ShutdownRequestReceived = false;
Index: clangd/ClangdLSPServer.cpp
===================================================================
--- clangd/ClangdLSPServer.cpp
+++ clangd/ClangdLSPServer.cpp
@@ -536,6 +536,17 @@
   PathRef File = Params.textDocument.uri.file();
   DraftMgr.removeDraft(File);
   Server->removeDocument(File);
+
+  {
+    std::lock_guard<std::mutex> Lock(FixItsMutex);
+    FixItsMap.erase(File);
+  }
+  // clangd will not send updates for this file anymore, so we empty out the
+  // list of diagnostics shown on the client (e.g. in the "Problems" pane of
+  // VSCode). Note that this cannot race with actual diagnostics responses
+  // because removeDocument() guarantees no diagnostic callbacks will be
+  // executed after it returns.
+  publishDiagnostics(URIForFile::canonicalize(File, /*TUPath=*/File), {});
 }
 
 void ClangdLSPServer::onDocumentOnTypeFormatting(
@@ -836,6 +847,16 @@
     reparseOpenedFiles();
 }
 
+void ClangdLSPServer::publishDiagnostics(
+    const URIForFile &File, std::vector<clangd::Diagnostic> Diagnostics) {
+  // Publish diagnostics.
+  notify("textDocument/publishDiagnostics",
+         llvm::json::Object{
+             {"uri", File},
+             {"diagnostics", std::move(Diagnostics)},
+         });
+}
+
 // FIXME: This function needs to be properly tested.
 void ClangdLSPServer::onChangeConfiguration(
     const DidChangeConfigurationParams &Params) {
@@ -978,17 +999,12 @@
 
   // Cache FixIts
   {
-    // FIXME(ibiryukov): should be deleted when documents are removed
     std::lock_guard<std::mutex> Lock(FixItsMutex);
     FixItsMap[File] = LocalFixIts;
   }
 
-  // Publish diagnostics.
-  notify("textDocument/publishDiagnostics",
-         llvm::json::Object{
-             {"uri", URI},
-             {"diagnostics", std::move(LSPDiagnostics)},
-         });
+  // Send a notification to the LSP client.
+  publishDiagnostics(URI, std::move(LSPDiagnostics));
 }
 
 void ClangdLSPServer::onFileUpdated(PathRef File, const TUStatus &Status) {
Index: test/clangd/diagnostics.test
===================================================================
--- test/clangd/diagnostics.test
+++ test/clangd/diagnostics.test
@@ -23,6 +23,15 @@
 # CHECK-NEXT:    "uri": "file://{{.*}}/foo.c"
 # CHECK-NEXT:  }
 ---
+{"jsonrpc":"2.0","id":2,"method":"sync","params":null}
+---
+{"jsonrpc":"2.0","method":"textDocument/didClose","params":{"textDocument":{"uri":"test:///foo.c"}}}
+#      CHECK:  "method": "textDocument/publishDiagnostics",
+# CHECK-NEXT:  "params": {
+# CHECK-NEXT:    "diagnostics": [],
+# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c"
+# CHECK-NEXT:  }
+---
 {"jsonrpc":"2.0","id":5,"method":"shutdown"}
 ---
 {"jsonrpc":"2.0","method":"exit"}