Index: lib/Frontend/ASTUnit.cpp
===================================================================
--- lib/Frontend/ASTUnit.cpp
+++ lib/Frontend/ASTUnit.cpp
@@ -1698,7 +1698,6 @@
   PreprocessorOptions &PPOpts = CI->getPreprocessorOpts();
   PPOpts.RemappedFilesKeepOriginalName = RemappedFilesKeepOriginalName;
   PPOpts.AllowPCHWithCompilerErrors = AllowPCHWithCompilerErrors;
-  PPOpts.GeneratePreamble = PrecompilePreambleAfterNParses != 0;
   PPOpts.SingleFileParseMode = SingleFileParse;
   
   // Override the resources path.
Index: lib/Frontend/PrecompiledPreamble.cpp
===================================================================
--- lib/Frontend/PrecompiledPreamble.cpp
+++ lib/Frontend/PrecompiledPreamble.cpp
@@ -234,6 +234,8 @@
   FrontendOpts.OutputFile = PreamblePCHFile->getFilePath();
   PreprocessorOpts.PrecompiledPreambleBytes.first = 0;
   PreprocessorOpts.PrecompiledPreambleBytes.second = false;
+  // Inform preprocessor to record conditional stack when building the preamble.
+  PreprocessorOpts.GeneratePreamble = true;
 
   // Create the compiler instance to use for building the precompiled preamble.
   std::unique_ptr<CompilerInstance> Clang(