diff --git a/clang-tools-extra/clangd/ParsedAST.cpp b/clang-tools-extra/clangd/ParsedAST.cpp
--- a/clang-tools-extra/clangd/ParsedAST.cpp
+++ b/clang-tools-extra/clangd/ParsedAST.cpp
@@ -424,15 +424,15 @@
     CTFinder.matchAST(Clang->getASTContext());
   }
 
+  // XXX: This is messy: clang-tidy checks flush some diagnostics at EOF.
+  // However Action->EndSourceFile() would destroy the ASTContext!
+  // So just inform the preprocessor of EOF, while keeping everything alive.
+  Clang->getPreprocessor().EndSourceFile();
   // UnitDiagsConsumer is local, we can not store it in CompilerInstance that
   // has a longer lifetime.
   Clang->getDiagnostics().setClient(new IgnoreDiagnostics);
   // CompilerInstance won't run this callback, do it directly.
   ASTDiags.EndSourceFile();
-  // XXX: This is messy: clang-tidy checks flush some diagnostics at EOF.
-  // However Action->EndSourceFile() would destroy the ASTContext!
-  // So just inform the preprocessor of EOF, while keeping everything alive.
-  Clang->getPreprocessor().EndSourceFile();
 
   std::vector<Diag> Diags = CompilerInvocationDiags;
   // Add diagnostics from the preamble, if any.
diff --git a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
--- a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
@@ -29,6 +29,8 @@
 namespace {
 
 using ::testing::_;
+using ::testing::AllOf;
+using ::testing::Contains;
 using ::testing::ElementsAre;
 using ::testing::Field;
 using ::testing::IsEmpty;
@@ -278,6 +280,23 @@
                   "use a trailing return type for this function")))));
 }
 
+TEST(DiagnosticsTest, ClangTidyEOF) {
+  // clang-format off
+  Annotations Test(R"cpp(
+  [[#]]include <b.h>
+  #include "a.h")cpp");
+  // clang-format on
+  auto TU = TestTU::withCode(Test.code());
+  TU.ExtraArgs = {"-isystem."};
+  TU.AdditionalFiles["a.h"] = TU.AdditionalFiles["b.h"] = "";
+  TU.ClangTidyChecks = "-*, llvm-include-order";
+  EXPECT_THAT(
+      TU.build().getDiagnostics(),
+      Contains(AllOf(Diag(Test.range(), "#includes are not sorted properly"),
+                     DiagSource(Diag::ClangTidy),
+                     DiagName("llvm-include-order"))));
+}
+
 TEST(DiagnosticTest, TemplatesInHeaders) {
   // Diagnostics from templates defined in headers are placed at the expansion.
   Annotations Main(R"cpp(