diff --git a/include/swift/ClangImporter/ClangImporter.h b/include/swift/ClangImporter/ClangImporter.h
index c0c8e823c2d..81dd56e2471 100644
--- a/include/swift/ClangImporter/ClangImporter.h
+++ b/include/swift/ClangImporter/ClangImporter.h
@@ -76,7 +76,8 @@ public:
                                StringRef moduleCachePath,
                                ArrayRef<std::string> importSearchPaths = {},
                                ArrayRef<std::string> frameworkSearchPaths = {},
-                               StringRef overrideResourceDir = StringRef());
+                               StringRef overrideResourceDir = StringRef(),
+                               ArrayRef<std::string> extraArgs = {});
 
   ClangImporter(const ClangImporter &) = delete;
   ClangImporter(ClangImporter &&) = delete;
diff --git a/include/swift/Frontend/Frontend.h b/include/swift/Frontend/Frontend.h
index 7856bce1c14..53fe83b383b 100644
--- a/include/swift/Frontend/Frontend.h
+++ b/include/swift/Frontend/Frontend.h
@@ -50,6 +50,7 @@ class CompilerInvocation {
   SmallVector<LinkLibrary, 4> LinkLibraries;
   std::string RuntimeIncludePath;
   std::string SDKPath;
+  std::vector<std::string> ExtraClangArgs;
 
   LangOptions LangOpts;
 
@@ -100,7 +101,7 @@ public:
     ImportSearchPaths = Paths;
   }
 
-  std::vector<std::string> getImportSearchPaths() const {
+  ArrayRef<std::string> getImportSearchPaths() const {
     return ImportSearchPaths;
   }
 
@@ -108,10 +109,18 @@ public:
     FrameworkSearchPaths = Paths;
   }
 
-  std::vector<std::string> getFrameworkSearchPaths() const {
+  ArrayRef<std::string> getFrameworkSearchPaths() const {
     return FrameworkSearchPaths;
   }
 
+  void setExtraClangArgs(const std::vector<std::string> &Args) {
+    ExtraClangArgs = Args;
+  }
+
+  ArrayRef<std::string> getExtraClangArgs() const {
+    return ExtraClangArgs;
+  }
+
   void addLinkLibrary(StringRef name, LibraryKind kind) {
     LinkLibraries.push_back({name, kind});
   }
diff --git a/lib/ClangImporter/ClangImporter.cpp b/lib/ClangImporter/ClangImporter.cpp
index c8a4907dafc..407cf4e1b9e 100644
--- a/lib/ClangImporter/ClangImporter.cpp
+++ b/lib/ClangImporter/ClangImporter.cpp
@@ -85,7 +85,8 @@ ClangImporter *ClangImporter::create(ASTContext &ctx, StringRef sdkroot,
                                      StringRef moduleCachePath,
                                      ArrayRef<std::string> importSearchPaths,
                                      ArrayRef<std::string> frameworkSearchPaths,
-                                     StringRef overrideResourceDir) {
+                                     StringRef overrideResourceDir,
+                                     ArrayRef<std::string> extraArgs) {
   std::unique_ptr<ClangImporter> importer(new ClangImporter(ctx));
 
   // Create a Clang diagnostics engine.
@@ -151,6 +152,10 @@ ClangImporter *ClangImporter::create(ASTContext &ctx, StringRef sdkroot,
     invocationArgStrs.push_back(overrideResourceDir);
   }
 
+  for (auto extraArg : extraArgs) {
+    invocationArgStrs.push_back(extraArg);
+  }
+
   std::vector<const char *> invocationArgs;
   for (auto &argStr : invocationArgStrs)
     invocationArgs.push_back(argStr.c_str());
diff --git a/lib/Frontend/Frontend.cpp b/lib/Frontend/Frontend.cpp
index bf94eadfaee..f421dd8a303 100644
--- a/lib/Frontend/Frontend.cpp
+++ b/lib/Frontend/Frontend.cpp
@@ -62,7 +62,7 @@ bool swift::CompilerInstance::setup(const CompilerInvocation &Invok) {
                      Invocation.getClangModuleCachePath(),
                      Invocation.getImportSearchPaths(),
                      Invocation.getFrameworkSearchPaths(),
-                     StringRef());
+                     StringRef(), Invocation.getExtraClangArgs());
     if (!clangImporter) {
       Diagnostics.diagnose(SourceLoc(), diag::error_clang_importer_create_fail);
       return true;