diff --git a/clang-tools-extra/clangd/IncludeCleaner.cpp b/clang-tools-extra/clangd/IncludeCleaner.cpp
--- a/clang-tools-extra/clangd/IncludeCleaner.cpp
+++ b/clang-tools-extra/clangd/IncludeCleaner.cpp
@@ -11,6 +11,7 @@
 #include "Diagnostics.h"
 #include "Headers.h"
 #include "ParsedAST.h"
+#include "Preamble.h"
 #include "Protocol.h"
 #include "SourceCode.h"
 #include "URI.h"
@@ -112,12 +113,12 @@
       return false;
     // Check if main file is the public interface for a private header. If so we
     // shouldn't diagnose it as unused.
-    if(auto PHeader = PI->getPublic(*FE); !PHeader.empty()) {
+    if (auto PHeader = PI->getPublic(*FE); !PHeader.empty()) {
       PHeader = PHeader.trim("<>\"");
       // Since most private -> public mappings happen in a verbatim way, we
       // check textually here. This might go wrong in presence of symlinks or
       // header mappings. But that's not different than rest of the places.
-      if(AST.tuPath().endswith(PHeader))
+      if (AST.tuPath().endswith(PHeader))
         return false;
     }
   }
@@ -360,6 +361,7 @@
   include_cleaner::Includes ConvertedIncludes =
       convertIncludes(SM, Includes.MainFileIncludes);
   const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID());
+  auto *PreamblePatch = PreamblePatch::getPatchEntry(AST.tuPath(), SM);
 
   std::vector<include_cleaner::SymbolReference> Macros =
       collectMacroReferences(AST);
@@ -374,7 +376,7 @@
         bool Satisfied = false;
         for (const auto &H : Providers) {
           if (H.kind() == include_cleaner::Header::Physical &&
-              H.physical() == MainFile) {
+              (H.physical() == MainFile || H.physical() == PreamblePatch)) {
             Satisfied = true;
             continue;
           }
diff --git a/clang-tools-extra/clangd/Preamble.h b/clang-tools-extra/clangd/Preamble.h
--- a/clang-tools-extra/clangd/Preamble.h
+++ b/clang-tools-extra/clangd/Preamble.h
@@ -30,6 +30,7 @@
 #include "clang-include-cleaner/Record.h"
 #include "index/CanonicalIncludes.h"
 #include "support/Path.h"
+#include "clang/Basic/SourceManager.h"
 #include "clang/Frontend/CompilerInvocation.h"
 #include "clang/Frontend/PrecompiledPreamble.h"
 #include "clang/Lex/Lexer.h"
@@ -37,8 +38,11 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 
+#include <cstddef>
+#include <functional>
 #include <memory>
 #include <string>
+#include <utility>
 #include <vector>
 
 namespace clang {
@@ -135,6 +139,10 @@
   static PreamblePatch createMacroPatch(llvm::StringRef FileName,
                                         const ParseInputs &Modified,
                                         const PreambleData &Baseline);
+  /// Returns the FileEntry for the preamble patch of MainFilePath in SM, if
+  /// any.
+  static const FileEntry *getPatchEntry(llvm::StringRef MainFilePath,
+                                        const SourceManager &SM);
 
   /// Adjusts CI (which compiles the modified inputs) to be used with the
   /// baseline preamble. This is done by inserting an artifical include to the
diff --git a/clang-tools-extra/clangd/Preamble.cpp b/clang-tools-extra/clangd/Preamble.cpp
--- a/clang-tools-extra/clangd/Preamble.cpp
+++ b/clang-tools-extra/clangd/Preamble.cpp
@@ -738,6 +738,14 @@
   return PatchedDiags;
 }
 
+static std::string getPatchName(llvm::StringRef FileName) {
+  // This shouldn't coincide with any real file name.
+  llvm::SmallString<128> PatchName;
+  llvm::sys::path::append(PatchName, llvm::sys::path::parent_path(FileName),
+                          PreamblePatch::HeaderName);
+  return PatchName.str().str();
+}
+
 PreamblePatch PreamblePatch::create(llvm::StringRef FileName,
                                     const ParseInputs &Modified,
                                     const PreambleData &Baseline,
@@ -776,11 +784,7 @@
 
   PreamblePatch PP;
   PP.Baseline = &Baseline;
-  // This shouldn't coincide with any real file name.
-  llvm::SmallString<128> PatchName;
-  llvm::sys::path::append(PatchName, llvm::sys::path::parent_path(FileName),
-                          PreamblePatch::HeaderName);
-  PP.PatchFileName = PatchName.str().str();
+  PP.PatchFileName = getPatchName(FileName);
   PP.ModifiedBounds = ModifiedScan->Bounds;
 
   llvm::raw_string_ostream Patch(PP.PatchContents);
@@ -921,5 +925,13 @@
     return Baseline->Macros;
   return PatchedMacros;
 }
+
+const FileEntry *PreamblePatch::getPatchEntry(llvm::StringRef MainFilePath,
+                                              const SourceManager &SM) {
+  auto PatchFilePath = getPatchName(MainFilePath);
+  if (auto File = SM.getFileManager().getFile(PatchFilePath))
+    return *File;
+  return nullptr;
+}
 } // namespace clangd
 } // namespace clang
diff --git a/clang-tools-extra/clangd/unittests/PreambleTests.cpp b/clang-tools-extra/clangd/unittests/PreambleTests.cpp
--- a/clang-tools-extra/clangd/unittests/PreambleTests.cpp
+++ b/clang-tools-extra/clangd/unittests/PreambleTests.cpp
@@ -666,6 +666,7 @@
   Config Cfg;
   Cfg.Diagnostics.AllowStalePreamble = true;
   Cfg.Diagnostics.UnusedIncludes = Config::IncludesPolicy::Strict;
+  Cfg.Diagnostics.MissingIncludes = Config::IncludesPolicy::Strict;
   WithContextValue WithCfg(Config::Key, std::move(Cfg));
 
   llvm::StringMap<std::string> AdditionalFiles;
@@ -699,6 +700,8 @@
   {
     Annotations Code("#define [[FOO]] 1\n");
     // Check ranges for notes.
+    // This also makes sure we don't generate missing-include diagnostics
+    // because macros are redefined in preamble-patch.
     Annotations NewCode(R"(#define BARXYZ 1
 #define $foo1[[FOO]] 1
 void foo();
@@ -866,6 +869,27 @@
   }
 }
 
+TEST(PreamblePatch, PatchFileEntry) {
+  Annotations Code(R"cpp(#define FOO)cpp");
+  Annotations NewCode(R"cpp(
+#define BAR
+#define FOO)cpp");
+  {
+    auto AST = createPatchedAST(Code.code(), Code.code());
+    EXPECT_EQ(
+        PreamblePatch::getPatchEntry(AST->tuPath(), AST->getSourceManager()),
+        nullptr);
+  }
+  {
+    auto AST = createPatchedAST(Code.code(), NewCode.code());
+    auto *FE =
+        PreamblePatch::getPatchEntry(AST->tuPath(), AST->getSourceManager());
+    ASSERT_NE(FE, nullptr);
+    EXPECT_THAT(FE->getName().str(),
+                testing::EndsWith(PreamblePatch::HeaderName.str()));
+  }
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang