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
@@ -428,15 +428,15 @@
     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.