Index: clang-tools-extra/clangd/CodeComplete.cpp
===================================================================
--- clang-tools-extra/clangd/CodeComplete.cpp
+++ clang-tools-extra/clangd/CodeComplete.cpp
@@ -1865,10 +1865,11 @@
   return (!Preamble || Opts.RunParser == CodeCompleteOptions::NeverParse)
              ? std::move(Flow).runWithoutSema(ParseInput.Contents, *Offset,
                                               *ParseInput.TFS)
-             : std::move(Flow).run({FileName, *Offset, *Preamble,
-                                    // We want to serve code completions with
-                                    // low latency, so don't bother patching.
-                                    /*PreamblePatch=*/llvm::None, ParseInput});
+             : std::move(Flow).run(
+                   {FileName, *Offset, *Preamble,
+                    /*PreamblePatch=*/
+                    PreamblePatch::create(FileName, ParseInput, *Preamble),
+                    ParseInput});
 }
 
 SignatureHelp signatureHelp(PathRef FileName, Position Pos,
Index: clang-tools-extra/clangd/Preamble.cpp
===================================================================
--- clang-tools-extra/clangd/Preamble.cpp
+++ clang-tools-extra/clangd/Preamble.cpp
@@ -142,10 +142,11 @@
   unsigned DirectiveLine;
   // Full text that's representing the directive, including the `#`.
   std::string Text;
+  SourceLocation Loc;
 
   bool operator==(const TextualPPDirective &RHS) const {
-    return std::tie(DirectiveLine, Text) ==
-           std::tie(RHS.DirectiveLine, RHS.Text);
+    return std::tie(DirectiveLine, Text, Loc) ==
+           std::tie(RHS.DirectiveLine, RHS.Text, RHS.Loc);
   }
 };
 
@@ -213,6 +214,7 @@
     TextualPPDirective &TD = TextualDirectives.back();
 
     const auto *MI = MD->getMacroInfo();
+    TD.Loc = MI->getDefinitionLoc();
     TD.Text =
         spellDirective("#define ",
                        CharSourceRange::getTokenRange(
Index: clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -3260,6 +3260,23 @@
     EXPECT_THAT(Results.Completions, UnorderedElementsAre(Labeled("BarExt")));
   }
 }
+
+TEST(CompletionTest, PreambleCodeComplete) {
+  llvm::StringLiteral Baseline = "\n#define MACRO 12\nint num = MACRO;";
+  llvm::StringLiteral ModifiedCC =
+      "#include \"header.h\"\n#define MACRO 12\nint num = MACRO; int num2 = M^";
+
+  Annotations Test(ModifiedCC);
+  auto BaselineTU = TestTU::withCode(Baseline);
+  auto ModifiedTU = TestTU::withCode(Test.code());
+
+  MockFS FS;
+  auto Inputs = ModifiedTU.inputs(FS);
+  auto Result = codeComplete(testPath(ModifiedTU.Filename), Test.point(),
+                             BaselineTU.preamble().get(), Inputs, {});
+  EXPECT_THAT(Result.Completions, Not(testing::IsEmpty()));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang
Index: clang-tools-extra/clangd/unittests/PreambleTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/PreambleTests.cpp
+++ clang-tools-extra/clangd/unittests/PreambleTests.cpp
@@ -546,6 +546,14 @@
   // Ensure they are dropeed when a patched preamble is used.
   EXPECT_FALSE(createPatchedAST("", Code)->getDiagnostics());
 }
+
+TEST(PreamblePatch, MacroLoc) {
+  llvm::StringLiteral Baseline = "\n#define MACRO 12\nint num = MACRO;";
+  llvm::StringLiteral Modified =
+      "#include \"header.h\"\n#define MACRO 12\nint num = MACRO;";
+  auto AST = createPatchedAST(Baseline, Modified);
+  ASSERT_TRUE(AST);
+}
 } // namespace
 } // namespace clangd
 } // namespace clang