diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index c81c81a..0bb5d87 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -383,6 +383,15 @@
            "doesn't support modules");
   }
 
+  // If we were asked to load any module map files, do so now.
+  for (const auto &Filename : CI.getFrontendOpts().ModuleMapFiles) {
+    if (auto *File = CI.getFileManager().getFile(Filename))
+      CI.getPreprocessor().getHeaderSearchInfo().loadModuleMapFile(
+          File, /*IsSystem*/false);
+    else
+      CI.getDiagnostics().Report(diag::err_module_map_not_found) << Filename;
+  }
+
   // If we were asked to load any module files, do so now.
   for (const auto &ModuleFile : CI.getFrontendOpts().ModuleFiles)
     if (!CI.loadModuleFile(ModuleFile))