diff --git a/include/clang/Basic/DiagnosticSerializationKinds.td b/include/clang/Basic/DiagnosticSerializationKinds.td
index f28f9983d0e0141a54e13195dbbff5ecd141bbd9..b0d352fc69348947806c0545344be9de18c28a11 100644
--- a/include/clang/Basic/DiagnosticSerializationKinds.td
+++ b/include/clang/Basic/DiagnosticSerializationKinds.td
@@ -66,9 +66,6 @@ def err_imported_module_relocated : Error<
 def err_module_different_modmap : Error<
     "module '%0' %select{uses|does not use}1 additional module map '%2'"
     "%select{| not}1 used when the module was built">;
-def err_module_system_change : Error<
-    "module '%0' %select{is|is not}1 a 'system' module, but "
-    "%select{was not|was}1 when the module was built">;
 def warn_module_conflict : Warning<
     "module '%0' conflicts with already-imported module '%1': %2">, 
     InGroup<ModuleConflict>;
diff --git a/include/clang/Lex/HeaderSearch.h b/include/clang/Lex/HeaderSearch.h
index 1fed331ff2df24074aaeff1d85873919b65d543f..28e7da37fd59e1741078911b11d0bf6a40ebf394 100644
--- a/include/clang/Lex/HeaderSearch.h
+++ b/include/clang/Lex/HeaderSearch.h
@@ -496,15 +496,11 @@ public:
   /// \param ModuleName The module whose module file name will be returned.
   ///
   /// \param ModuleMapPath A path that when combined with \c ModuleName
-  /// and \p IsSystem uniquely identifies this module. See Module::ModuleMap.
-  ///
-  /// \param IsSystem Whether the \p ModuleName is a system module, which may
-  /// depend on how header search paths were specified.
+  /// uniquely identifies this module. See Module::ModuleMap.
   ///
   /// \returns The name of the module file that corresponds to this module,
   /// or an empty string if this module does not correspond to any module file.
-  std::string getModuleFileName(StringRef ModuleName, StringRef ModuleMapPath,
-                                bool IsSystem);
+  std::string getModuleFileName(StringRef ModuleName, StringRef ModuleMapPath);
 
   /// \brief Lookup a module Search for a module with the given name.
   ///
diff --git a/lib/Frontend/FrontendActions.cpp b/lib/Frontend/FrontendActions.cpp
index c8673e50a058661b76d4c0db12ee8be7eb0de13b..a55a3257851f8e2b81c4fca8c2d6e864b60a7463 100644
--- a/lib/Frontend/FrontendActions.cpp
+++ b/lib/Frontend/FrontendActions.cpp
@@ -366,7 +366,7 @@ bool GenerateModuleAction::ComputeASTConsumerArguments(CompilerInstance &CI,
     HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
     CI.getFrontendOpts().OutputFile =
         HS.getModuleFileName(CI.getLangOpts().CurrentModule,
-                             ModuleMapForUniquing->getName(), IsSystem);
+                             ModuleMapForUniquing->getName());
   }
   
   // We use createOutputFile here because this is exposed via libclang, and we
diff --git a/lib/Lex/HeaderSearch.cpp b/lib/Lex/HeaderSearch.cpp
index f76d851ac6c9575575e6d0c3cdd22054a8a1d3a5..d6b255fb014e05ab285ed3e953b57138292c1162 100644
--- a/lib/Lex/HeaderSearch.cpp
+++ b/lib/Lex/HeaderSearch.cpp
@@ -115,13 +115,11 @@ const HeaderMap *HeaderSearch::CreateHeaderMap(const FileEntry *FE) {
 std::string HeaderSearch::getModuleFileName(Module *Module) {
   const FileEntry *ModuleMap =
       getModuleMap().getModuleMapFileForUniquing(Module);
-  return getModuleFileName(Module->Name, ModuleMap->getName(),
-                           Module->IsSystem);
+  return getModuleFileName(Module->Name, ModuleMap->getName());
 }
 
 std::string HeaderSearch::getModuleFileName(StringRef ModuleName,
-                                            StringRef ModuleMapPath,
-                                            bool IsSystem) {
+                                            StringRef ModuleMapPath) {
   // If we don't have a module cache path, we can't do anything.
   if (ModuleCachePath.empty()) 
     return std::string();
@@ -149,10 +147,6 @@ std::string HeaderSearch::getModuleFileName(StringRef ModuleName,
     llvm::hash_code Hash =
         llvm::hash_combine(DirName.lower(), FileName.lower());
 
-    // Hash the IsSystem bit, since changing search paths can change whether a
-    // module is considered 'system' or not.
-    Hash = llvm::hash_combine(Hash, IsSystem);
-
     SmallString<128> HashStr;
     llvm::APInt(64, size_t(Hash)).toStringUnsigned(HashStr, /*Radix*/36);
     llvm::sys::path::append(Result, ModuleName + "-" + HashStr.str() + ".pcm");
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 7774b7b1c6e74024d9928bd9ecb272bfcb02e0f6..bb6a450222d3163a4737bbb7609a613f7c8b5e7d 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -3468,13 +3468,6 @@ ASTReader::ReadModuleMapFileBlock(RecordData &Record, ModuleFile &F,
           << F.ModuleName << /*not new*/1 << ModMap->getName();
       return OutOfDate;
     }
-
-    // Check whether the 'IsSystem' bit changed.
-    if (M->IsSystem != static_cast<bool>(Record[Idx])) {
-      if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
-        Diag(diag::err_module_system_change) << F.ModuleName << M->IsSystem;
-      return OutOfDate;
-    }
   }
 
   if (Listener)
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index c0ce5f8e5ca7715aa0a06ac3a3331251ff617b06..07d5d29e44b0d41df644ea3e70a8c3a66a4ed6fc 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -1216,7 +1216,6 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
       Record.push_back(0);
     }
 
-    Record.push_back(WritingModule->IsSystem);
     Stream.EmitRecord(MODULE_MAP_FILE, Record);
   }
 
diff --git a/test/Modules/modules-with-same-name.m b/test/Modules/modules-with-same-name.m
index 3c5f88b18ac3a7f48df8db856f5b26f98b8cb8ba..d362f756a60a885733b0ae577938bf7c9e16ce81 100644
--- a/test/Modules/modules-with-same-name.m
+++ b/test/Modules/modules-with-same-name.m
@@ -21,14 +21,6 @@
 // Confirm that we still have three pcm files, since DependsOnA will be rebuilt
 // RUN: find %t -name "*.pcm" | count 3
 
-// DependsOnA, using A from path 2, as a system path
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fmodules-ignore-macro=EXPECTED_PATH -fmodules-ignore-macro=DIRECT -fsyntax-only %s -I %S/Inputs/modules-with-same-name/DependsOnA -isystem %S/Inputs/modules-with-same-name/path2/A -DEXPECTED_PATH=2 -Rmodule-build 2> %t.log
-// Confirm that we built a new module for A
-// RUN: FileCheck %s < %t.log
-// CHECK: building module 'DependsOnA'
-// CHECK: building module 'A'
-// RUN: find %t -name "*.pcm" | count 4
-
 #ifdef DIRECT
 @import A;
 #else