Index: include/clang/Frontend/ChainedDiagnosticConsumer.h
===================================================================
--- include/clang/Frontend/ChainedDiagnosticConsumer.h	(revision 221793)
+++ include/clang/Frontend/ChainedDiagnosticConsumer.h	(working copy)
@@ -22,14 +22,21 @@
 /// diagnostics should be included in counts.
 class ChainedDiagnosticConsumer : public DiagnosticConsumer {
   virtual void anchor();
-  std::unique_ptr<DiagnosticConsumer> Primary;
+  std::unique_ptr<DiagnosticConsumer> OwningPrimary;
+  DiagnosticConsumer *Primary;
   std::unique_ptr<DiagnosticConsumer> Secondary;
 
 public:
   ChainedDiagnosticConsumer(std::unique_ptr<DiagnosticConsumer> Primary,
                             std::unique_ptr<DiagnosticConsumer> Secondary)
-      : Primary(std::move(Primary)), Secondary(std::move(Secondary)) {}
+      : OwningPrimary(std::move(Primary)), Primary(OwningPrimary.get()),
+        Secondary(std::move(Secondary)) {}
 
+  /// \brief Construct without taking ownership of \c Primary.
+  ChainedDiagnosticConsumer(DiagnosticConsumer *Primary,
+                            std::unique_ptr<DiagnosticConsumer> Secondary)
+      : Primary(Primary), Secondary(std::move(Secondary)) {}
+
   void BeginSourceFile(const LangOptions &LO,
                        const Preprocessor *PP) override {
     Primary->BeginSourceFile(LO, PP);
Index: lib/Frontend/CompilerInstance.cpp
===================================================================
--- lib/Frontend/CompilerInstance.cpp	(revision 221793)
+++ lib/Frontend/CompilerInstance.cpp	(working copy)
@@ -170,10 +170,14 @@
   auto SerializedConsumer =
       clang::serialized_diags::create(OutputFile, DiagOpts);
 
-  assert(Diags.ownsClient());
-  Diags.setClient(new ChainedDiagnosticConsumer(
-      std::unique_ptr<DiagnosticConsumer>(Diags.takeClient()),
-      std::move(SerializedConsumer)));
+  if (Diags.ownsClient()) {
+    Diags.setClient(new ChainedDiagnosticConsumer(
+        std::unique_ptr<DiagnosticConsumer>(Diags.takeClient()),
+        std::move(SerializedConsumer)));
+  } else {
+    Diags.setClient(new ChainedDiagnosticConsumer(
+        Diags.takeClient(), std::move(SerializedConsumer)));
+  }
 }
 
 void CompilerInstance::createDiagnostics(DiagnosticConsumer *Client,