diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 61f4e86..a2540bc 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -370,7 +370,8 @@
 SourceManager::SourceManager(DiagnosticsEngine &Diag, FileManager &FileMgr)
   : Diag(Diag), FileMgr(FileMgr), OverridenFilesKeepOriginalName(true),
     ExternalSLocEntries(0), LineTable(0), NumLinearScans(0),
-    NumBinaryProbes(0), FakeBufferForRecovery(0) {
+    NumBinaryProbes(0), FakeBufferForRecovery(0),
+    FakeContentCacheForRecovery(0) {
   clearIDTables();
   Diag.setSourceManager(this);
 }
@@ -396,6 +397,7 @@
   }
   
   delete FakeBufferForRecovery;
+  delete FakeContentCacheForRecovery;
 
   for (llvm::DenseMap<FileID, MacroArgsMap *>::iterator
          I = MacroArgsCacheMap.begin(),E = MacroArgsCacheMap.end(); I!=E; ++I) {
@@ -469,6 +471,25 @@
   return Entry;
 }
 
+const SrcMgr::SLocEntry &SourceManager::loadSLocEntry(unsigned Index,
+                                                      bool *Invalid) const {
+  assert(!SLocEntryLoaded[Index]);
+  if (ExternalSLocEntries->ReadSLocEntry(-(static_cast<int>(Index) + 2))) {
+    if (Invalid)
+      *Invalid = true;
+    // If the file of the SLocEntry changed we could still have loaded it.
+    if (!SLocEntryLoaded[Index]) {
+      // Try to recover; create a SLocEntry so the rest of clang can handle it.
+      LoadedSLocEntryTable[Index] = SLocEntry::get(0,
+                                 FileInfo::get(SourceLocation(),
+                                               getFakeContentCacheForRecovery(),
+                                               SrcMgr::C_User));
+    }
+  }
+
+  return LoadedSLocEntryTable[Index];
+}
+
 std::pair<int, unsigned>
 SourceManager::AllocateLoadedSLocEntries(unsigned NumSLocEntries,
                                          unsigned TotalSize) {
@@ -491,6 +512,18 @@
   return FakeBufferForRecovery;
 }
 
+/// \brief As part of recovering from missing or changed content, produce a
+/// fake content cache.
+const SrcMgr::ContentCache *
+SourceManager::getFakeContentCacheForRecovery() const {
+  if (!FakeContentCacheForRecovery) {
+    FakeContentCacheForRecovery = new ContentCache();
+    FakeContentCacheForRecovery->replaceBuffer(getFakeBufferForRecovery(),
+                                               /*DoNotFree=*/true);
+  }
+  return FakeContentCacheForRecovery;
+}
+
 //===----------------------------------------------------------------------===//
 // Methods to create new FileID's and macro expansions.
 //===----------------------------------------------------------------------===//
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 75b5d68..dde54d6 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -1111,6 +1111,10 @@
       return Failure;
     }
 
+    // We will detect whether a file changed and return 'Failure' for it, but
+    // we will also try to fail gracefully by setting up the SLocEntry.
+    ASTReader::ASTReadResult Result = Success;
+
     bool OverriddenBuffer = Record[6];
     
     std::string OrigFilename(BlobStart, BlobStart + BlobLen);
@@ -1149,7 +1153,7 @@
 #endif
         )) {
       Error(diag::err_fe_pch_file_modified, Filename);
-      return Failure;
+      Result = Failure;
     }
 
     SourceLocation IncludeLoc = ReadSourceLocation(*F, Record[1]);
@@ -1193,6 +1197,9 @@
                                            Filename);
       SourceMgr.overrideFileContents(File, Buffer);
     }
+
+    if (Result == Failure)
+      return Failure;
     break;
   }