diff --git a/clang/include/clang/Serialization/ASTWriter.h b/clang/include/clang/Serialization/ASTWriter.h
index 2c747d8ea844..bad5c379bcbf 100644
--- a/clang/include/clang/Serialization/ASTWriter.h
+++ b/clang/include/clang/Serialization/ASTWriter.h
@@ -146,7 +146,7 @@ private:
   /// the declaration's ID.
   std::vector<serialization::DeclOffset> DeclOffsets;
 
-  /// \brief Vector of pairs of raw location/DeclID.
+  /// \brief Sorted (by file offset) vector of pairs of file offset/DeclID.
   typedef SmallVector<std::pair<unsigned, serialization::DeclID>, 64>
     LocDeclIDsTy;
   struct DeclIDInFileInfo {
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 0c9f0a1247cd..1b44baa9ce53 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3501,7 +3501,9 @@ void ASTWriter::associateDeclWithFile(const Decl *D, DeclID ID) {
   SourceManager &SM = Context->getSourceManager();
   SourceLocation FileLoc = SM.getFileLoc(Loc);
   assert(SM.isLocalSourceLocation(FileLoc));
-  FileID FID = SM.getFileID(FileLoc);
+  FileID FID;
+  unsigned Offset;
+  llvm::tie(FID, Offset) = SM.getDecomposedLoc(FileLoc);
   if (FID.isInvalid())
     return;
   const SrcMgr::SLocEntry *Entry = &SM.getSLocEntry(FID);
@@ -3511,11 +3513,10 @@ void ASTWriter::associateDeclWithFile(const Decl *D, DeclID ID) {
   if (!Info)
     Info = new DeclIDInFileInfo();
 
-  unsigned RawLoc = FileLoc.getRawEncoding();
-  std::pair<unsigned, serialization::DeclID> LocDecl(RawLoc, ID);
+  std::pair<unsigned, serialization::DeclID> LocDecl(Offset, ID);
   LocDeclIDsTy &Decls = Info->DeclIDs;
 
-  if (Decls.empty() || Decls.back().first <= RawLoc) {
+  if (Decls.empty() || Decls.back().first <= Offset) {
     Decls.push_back(LocDecl);
     return;
   }