diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 84d837d..9a4bcc2 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1641,6 +1641,14 @@
   } else if (ModuleName == getLangOpts().CurrentModule) {
     // This is the module we're building. 
     Module = PP->getHeaderSearchInfo().lookupModule(ModuleName);
+    /// FIXME: perhaps we should (a) look for a module using the module name
+    //  to file map (PrebuiltModuleFiles) and (b) diagnose if still not found?
+    //if (Module == nullptr) {
+    //  getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
+    //    << ModuleName;
+    //  ModuleBuildFailed = true;
+    //  return ModuleLoadResult();
+    //}
     Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;
   } else {
     // Search for a module with the given name.
@@ -1662,16 +1670,17 @@
     }
 
     // Try to load the module from the prebuilt module path.
-    if (Source == ModuleNotFound && !HSOpts.PrebuiltModulePaths.empty()) {
-      ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(
-          ModuleName, "", /*UsePrebuiltPath*/ true);
+    if (Source == ModuleNotFound && (!HSOpts.PrebuiltModuleFiles.empty() ||
+                                     !HSOpts.PrebuiltModulePaths.empty())) {
+      ModuleFileName =
+        PP->getHeaderSearchInfo().getPrebuiltModuleFileName(ModuleName);
       if (!ModuleFileName.empty())
         Source = PrebuiltModulePath;
     }
 
     // Try to load the module from the module cache.
     if (Source == ModuleNotFound && Module) {
-      ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(Module);
+      ModuleFileName = PP->getHeaderSearchInfo().getCachedModuleFileName(Module);
       Source = ModuleCache;
     }