diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 8083fe0..ab866a2 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -2234,7 +2234,7 @@
 // it.
 static void addSystemInclude(const ArgList &DriverArgs, ArgStringList &CC1Args,
                              const Twine &Path) {
-  CC1Args.push_back("-isystem");
+  CC1Args.push_back("-internal-isystem");
   CC1Args.push_back(DriverArgs.MakeArgString(Path));
 }
 
@@ -2246,7 +2246,7 @@
                               ArrayRef<StringRef> Paths) {
   for (ArrayRef<StringRef>::iterator I = Paths.begin(), E = Paths.end();
        I != E; ++I) {
-    CC1Args.push_back("-isystem");
+    CC1Args.push_back("-internal-isystem");
     CC1Args.push_back(DriverArgs.MakeArgString(*I));
   }
 }
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 399e0ca..1829d7d 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -575,10 +575,16 @@
         break;
       }
     } else {
-      if (E.Group != frontend::Angled && E.Group != frontend::System)
-        llvm::report_fatal_error("Invalid option set!");
-      Res.push_back(E.Group == frontend::Angled ? "-iwithprefixbefore" :
-                    "-iwithprefix");
+      if (E.IsInternal) {
+        assert(E.Group == frontend::System && "Unexpected header search group");
+        Res.push_back(E.ImplicitExternC ? "-internal-externc-isystem"
+                                        : "-internal-isystem");
+      } else {
+        if (E.Group != frontend::Angled && E.Group != frontend::System)
+          llvm::report_fatal_error("Invalid option set!");
+        Res.push_back(E.Group == frontend::Angled ? "-iwithprefixbefore" :
+                      "-iwithprefix");
+      }
     }
     Res.push_back(E.Path);
   }
@@ -1483,6 +1489,15 @@
        ie = Args.filtered_end(); it != ie; ++it)
     Opts.AddPath((*it)->getValue(Args), frontend::ObjCXXSystem, true, false,
                  true);
+
+  // Add the internal paths from a driver that detects standard include paths.
+  for (arg_iterator I = Args.filtered_begin(OPT_internal_isystem,
+                                            OPT_internal_externc_isystem),
+                    E = Args.filtered_end();
+       I != E; ++I)
+    Opts.AddPath((*I)->getValue(Args), frontend::System,
+                 false, false, false, /*IsInternal=*/true,
+                 (*I)->getOption().matches(OPT_internal_externc_isystem));
 }
 
 void CompilerInvocation::setLangDefaults(LangOptions &Opts, InputKind IK,
diff --git a/lib/Frontend/InitHeaderSearch.cpp b/lib/Frontend/InitHeaderSearch.cpp
index 8a7683a..decf345 100644
--- a/lib/Frontend/InitHeaderSearch.cpp
+++ b/lib/Frontend/InitHeaderSearch.cpp
@@ -925,8 +925,8 @@
   // Add the user defined entries.
   for (unsigned i = 0, e = HSOpts.UserEntries.size(); i != e; ++i) {
     const HeaderSearchOptions::Entry &E = HSOpts.UserEntries[i];
-    Init.AddPath(E.Path, E.Group, false, E.IsUserSupplied, E.IsFramework,
-                 E.IgnoreSysRoot);
+    Init.AddPath(E.Path, E.Group, !E.ImplicitExternC, E.IsUserSupplied,
+                 E.IsFramework, E.IgnoreSysRoot);
   }
 
   Init.AddDefaultIncludePaths(Lang, Triple, HSOpts);