diff --git a/include/swift/ClangImporter/ClangImporter.h b/include/swift/ClangImporter/ClangImporter.h
index cf96a7127ecd4..5358961157ee4 100644
--- a/include/swift/ClangImporter/ClangImporter.h
+++ b/include/swift/ClangImporter/ClangImporter.h
@@ -160,6 +160,8 @@ class ClangImporter final : public ClangModuleLoader {
 private:
   Implementation &Impl;
 
+  bool requiresBuiltinHeadersInSystemModules = false;
+
   ClangImporter(ASTContext &ctx,
                 DependencyTracker *tracker,
                 DWARFImporterDelegate *dwarfImporterDelegate);
@@ -198,14 +200,18 @@ class ClangImporter final : public ClangModuleLoader {
          DWARFImporterDelegate *dwarfImporterDelegate = nullptr,
          bool ignoreFileMapping = false);
 
-  static std::vector<std::string>
+  std::vector<std::string>
   getClangDriverArguments(ASTContext &ctx, bool ignoreClangTarget = false);
 
-  static std::optional<std::vector<std::string>>
-  getClangCC1Arguments(ClangImporter *importer, ASTContext &ctx,
+  std::optional<std::vector<std::string>>
+  getClangCC1Arguments(ASTContext &ctx,
                        llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
                        bool ignoreClangTarget = false);
 
+  std::vector<std::string>
+  getClangDepScanningInvocationArguments(ASTContext &ctx,
+      std::optional<StringRef> sourceFileName = std::nullopt);
+
   static std::unique_ptr<clang::CompilerInvocation>
   createClangInvocation(ClangImporter *importer,
                         const ClangImporterOptions &importerOpts,
diff --git a/lib/ClangImporter/ClangImporter.cpp b/lib/ClangImporter/ClangImporter.cpp
index a32c529832bec..0bdf9ca765a0a 100644
--- a/lib/ClangImporter/ClangImporter.cpp
+++ b/lib/ClangImporter/ClangImporter.cpp
@@ -789,7 +789,8 @@ getEmbedBitcodeInvocationArguments(std::vector<std::string> &invocationArgStrs,
 void
 importer::addCommonInvocationArguments(
     std::vector<std::string> &invocationArgStrs,
-    ASTContext &ctx, bool ignoreClangTarget) {
+    ASTContext &ctx, bool requiresBuiltinHeadersInSystemModules,
+    bool ignoreClangTarget) {
   using ImporterImpl = ClangImporter::Implementation;
   llvm::Triple triple = ctx.LangOpts.Target;
   // Use clang specific target triple if given.
@@ -957,6 +958,16 @@ importer::addCommonInvocationArguments(
       }
     }
   }
+
+  for (auto &overlay : searchPathOpts.VFSOverlayFiles) {
+    invocationArgStrs.push_back("-ivfsoverlay");
+    invocationArgStrs.push_back(overlay);
+  }
+
+  if (requiresBuiltinHeadersInSystemModules) {
+    invocationArgStrs.push_back("-Xclang");
+    invocationArgStrs.push_back("-fbuiltin-headers-in-system-modules");
+  }
 }
 
 bool ClangImporter::canReadPCH(StringRef PCHFilename) {
@@ -1140,13 +1151,13 @@ ClangImporter::getClangDriverArguments(ASTContext &ctx, bool ignoreClangTarget)
     getEmbedBitcodeInvocationArguments(invocationArgStrs, ctx);
     break;
   }
-  addCommonInvocationArguments(invocationArgStrs, ctx, ignoreClangTarget);
+  addCommonInvocationArguments(invocationArgStrs, ctx,
+      requiresBuiltinHeadersInSystemModules, ignoreClangTarget);
   return invocationArgStrs;
 }
 
 std::optional<std::vector<std::string>> ClangImporter::getClangCC1Arguments(
-    ClangImporter *importer, ASTContext &ctx,
-    llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
+    ASTContext &ctx, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
     bool ignoreClangTarget) {
   std::unique_ptr<clang::CompilerInvocation> CI;
 
@@ -1161,7 +1172,7 @@ std::optional<std::vector<std::string>> ClangImporter::getClangCC1Arguments(
   llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> tempDiagOpts{
       new clang::DiagnosticOptions};
   auto *tempDiagClient =
-      new ClangDiagnosticConsumer(importer->Impl, *tempDiagOpts,
+      new ClangDiagnosticConsumer(Impl, *tempDiagOpts,
                                   ctx.ClangImporterOpts.DumpClangDiagnostics);
   auto clangDiags = clang::CompilerInstance::createDiagnostics(
       tempDiagOpts.get(), tempDiagClient,
@@ -1248,20 +1259,18 @@ std::optional<std::vector<std::string>> ClangImporter::getClangCC1Arguments(
   // resilient and provide a module even if there were building it.
   auto TempVFS = clang::createVFSFromCompilerInvocation(
       *CI, *clangDiags,
-      VFS ? VFS : importer->Impl.SwiftContext.SourceMgr.getFileSystem());
+      VFS ? VFS : Impl.SwiftContext.SourceMgr.getFileSystem());
 
   std::vector<std::string> FilteredModuleMapFiles;
   for (auto ModuleMapFile : CI->getFrontendOpts().ModuleMapFiles) {
     if (ctx.ClangImporterOpts.HasClangIncludeTreeRoot) {
       // There is no need to add any module map file here. Issue a warning and
       // drop the option.
-      importer->Impl.diagnose(SourceLoc(), diag::module_map_ignored,
-                              ModuleMapFile);
+      Impl.diagnose(SourceLoc(), diag::module_map_ignored, ModuleMapFile);
     } else if (TempVFS->exists(ModuleMapFile)) {
       FilteredModuleMapFiles.push_back(ModuleMapFile);
     } else {
-      importer->Impl.diagnose(SourceLoc(), diag::module_map_not_found,
-                              ModuleMapFile);
+      Impl.diagnose(SourceLoc(), diag::module_map_not_found, ModuleMapFile);
     }
   }
   CI->getFrontendOpts().ModuleMapFiles = FilteredModuleMapFiles;
@@ -1330,6 +1339,9 @@ ClangImporter::create(ASTContext &ctx,
   ClangInvocationFileMapping fileMapping =
     getClangInvocationFileMapping(ctx, nullptr, ignoreFileMapping);
 
+  importer->requiresBuiltinHeadersInSystemModules =
+      fileMapping.requiresBuiltinHeadersInSystemModules;
+
   // Avoid creating indirect file system when using include tree.
   if (!ctx.ClangImporterOpts.HasClangIncludeTreeRoot) {
     // Wrap Swift's FS to allow Clang to override the working directory
@@ -1370,14 +1382,11 @@ ClangImporter::create(ASTContext &ctx,
 
   // Create a new Clang compiler invocation.
   {
-    if (auto ClangArgs = getClangCC1Arguments(importer.get(), ctx, VFS))
+    if (auto ClangArgs = importer->getClangCC1Arguments(ctx, VFS))
       importer->Impl.ClangArgs = *ClangArgs;
     else
       return nullptr;
 
-    if (fileMapping.requiresBuiltinHeadersInSystemModules)
-      importer->Impl.ClangArgs.push_back("-fbuiltin-headers-in-system-modules");
-
     ArrayRef<std::string> invocationArgStrs = importer->Impl.ClangArgs;
     if (importerOpts.DumpClangDiagnostics) {
       llvm::errs() << "clang importer cc1 args: '";
@@ -1465,8 +1474,7 @@ ClangImporter::create(ASTContext &ctx,
   if (ctx.LangOpts.ClangTarget.has_value()) {
     // If '-clang-target' is set, create a mock invocation with the Swift triple
     // to configure CodeGen and Target options for Swift compilation.
-    auto swiftTargetClangArgs =
-        getClangCC1Arguments(importer.get(), ctx, VFS, true);
+    auto swiftTargetClangArgs = importer->getClangCC1Arguments(ctx, VFS, true);
     if (!swiftTargetClangArgs)
       return nullptr;
     auto swiftTargetClangInvocation = createClangInvocation(
diff --git a/lib/ClangImporter/ClangModuleDependencyScanner.cpp b/lib/ClangImporter/ClangModuleDependencyScanner.cpp
index 37e702ca29095..4726a488750a3 100644
--- a/lib/ClangImporter/ClangModuleDependencyScanner.cpp
+++ b/lib/ClangImporter/ClangModuleDependencyScanner.cpp
@@ -70,10 +70,9 @@ static void addScannerPrefixMapperInvocationArguments(
 }
 
 /// Create the command line for Clang dependency scanning.
-static std::vector<std::string> getClangDepScanningInvocationArguments(
-    ASTContext &ctx, std::optional<StringRef> sourceFileName = std::nullopt) {
-  std::vector<std::string> commandLineArgs =
-      ClangImporter::getClangDriverArguments(ctx);
+std::vector<std::string> ClangImporter::getClangDepScanningInvocationArguments(
+    ASTContext &ctx, std::optional<StringRef> sourceFileName) {
+  std::vector<std::string> commandLineArgs = getClangDriverArguments(ctx);
   addScannerPrefixMapperInvocationArguments(commandLineArgs, ctx);
 
   auto sourceFilePos = std::find(
diff --git a/lib/ClangImporter/ImporterImpl.h b/lib/ClangImporter/ImporterImpl.h
index 08a44e1d797b3..a8b72279efd44 100644
--- a/lib/ClangImporter/ImporterImpl.h
+++ b/lib/ClangImporter/ImporterImpl.h
@@ -1914,6 +1914,7 @@ void getNormalInvocationArguments(std::vector<std::string> &invocationArgStrs,
 /// Add command-line arguments common to all imports of Clang code.
 void addCommonInvocationArguments(std::vector<std::string> &invocationArgStrs,
                                   ASTContext &ctx,
+                                  bool requiresBuiltinHeadersInSystemModules,
                                   bool ignoreClangTarget);
 
 /// Finds a particular kind of nominal by looking through typealiases.
diff --git a/test/ScanDependencies/win-crt.swift b/test/ScanDependencies/win-crt.swift
new file mode 100644
index 0000000000000..0b1055d4087c3
--- /dev/null
+++ b/test/ScanDependencies/win-crt.swift
@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -scan-dependencies -Xcc -v %s -o - | %validate-json | %FileCheck %s
+
+// We want to explicitly import WinSDK's CRT.
+// REQUIRES: OS=windows-msvc
+
+import CRT
+
+// CHECK:        "modulePath": "{{.*}}\\ucrt-{{.*}}.pcm",
+// CHECK-NEXT:   "sourceFiles": [
+// CHECK-NEXT:      "{{.*}}\\ucrt\\module.modulemap"