diff --git a/clang/include/clang/Interpreter/Interpreter.h b/clang/include/clang/Interpreter/Interpreter.h
--- a/clang/include/clang/Interpreter/Interpreter.h
+++ b/clang/include/clang/Interpreter/Interpreter.h
@@ -69,6 +69,8 @@
     return llvm::Error::success();
   }
 
+  void Restore(PartialTranslationUnit &PTU);
+
   /// \returns the \c JITTargetAddress of a \c GlobalDecl. This interface uses
   /// the CodeGenModule's internal mangling cache to avoid recomputing the
   /// mangled name.
diff --git a/clang/lib/Interpreter/IncrementalParser.h b/clang/lib/Interpreter/IncrementalParser.h
--- a/clang/lib/Interpreter/IncrementalParser.h
+++ b/clang/lib/Interpreter/IncrementalParser.h
@@ -72,6 +72,8 @@
   ///\returns the mangled name of a \c GD.
   llvm::StringRef GetMangledName(GlobalDecl GD) const;
 
+  void Restore(PartialTranslationUnit &PTU);
+
 private:
   llvm::Expected<PartialTranslationUnit &> ParseOrWrapTopLevelDecl();
 };
diff --git a/clang/lib/Interpreter/IncrementalParser.cpp b/clang/lib/Interpreter/IncrementalParser.cpp
--- a/clang/lib/Interpreter/IncrementalParser.cpp
+++ b/clang/lib/Interpreter/IncrementalParser.cpp
@@ -293,6 +293,24 @@
   return PTU;
 }
 
+void IncrementalParser::Restore(PartialTranslationUnit &PTU) {
+  TranslationUnitDecl *MostRecentTU = PTU.TUPart;
+  TranslationUnitDecl *FirstTU = MostRecentTU->getFirstDecl();
+  if (StoredDeclsMap *Map = FirstTU->getLookupPtr()) {
+    for (auto I = Map->begin(); I != Map->end(); ++I) {
+      StoredDeclsList &List = I->second;
+      DeclContextLookupResult R = List.getLookupResult();
+      for (NamedDecl *D : R) {
+        if (D->getTranslationUnitDecl() == MostRecentTU) {
+          List.remove(D);
+        }
+      }
+      if (List.isNull())
+        Map->erase(I);
+    }
+  }
+}
+
 llvm::StringRef IncrementalParser::GetMangledName(GlobalDecl GD) const {
   CodeGenerator *CG = getCodeGen(Act.get());
   assert(CG);
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -228,6 +228,10 @@
   return llvm::Error::success();
 }
 
+void Interpreter::Restore(PartialTranslationUnit &PTU) {
+  IncrParser->Restore(PTU);
+}
+
 llvm::Expected<llvm::JITTargetAddress>
 Interpreter::getSymbolAddress(GlobalDecl GD) const {
   if (!IncrExecutor)