diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index cdf921d..85ed3ba 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -2612,6 +2612,16 @@
 TagDecl *TagDecl::getDefinition() const {
   if (isCompleteDefinition())
     return const_cast<TagDecl *>(this);
+
+  // If it's possible for us to have an out-of-date definition, check now.
+  if (MayHaveOutOfDateDef) {
+    if (IdentifierInfo *II = getIdentifier()) {
+      if (II->isOutOfDate()) {
+        updateOutOfDate(*II);
+      }
+    }
+  }
+
   if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(this))
     return CXXRD->getDefinition();
 
@@ -2668,14 +2678,17 @@
                            bool IsScopedUsingClassTag, bool IsFixed) {
   EnumDecl *Enum = new (C) EnumDecl(DC, StartLoc, IdLoc, Id, PrevDecl,
                                     IsScoped, IsScopedUsingClassTag, IsFixed);
+  Enum->MayHaveOutOfDateDef = C.getLangOpts().Modules;
   C.getTypeDeclType(Enum, PrevDecl);
   return Enum;
 }
 
 EnumDecl *EnumDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, sizeof(EnumDecl));
-  return new (Mem) EnumDecl(0, SourceLocation(), SourceLocation(), 0, 0,
-                            false, false, false);
+  EnumDecl *Enum = new (Mem) EnumDecl(0, SourceLocation(), SourceLocation(),
+                                      0, 0, false, false, false);
+  Enum->MayHaveOutOfDateDef = C.getLangOpts().Modules;
+  return Enum;
 }
 
 void EnumDecl::completeDefinition(QualType NewType,
@@ -2743,14 +2756,18 @@
                                IdentifierInfo *Id, RecordDecl* PrevDecl) {
   RecordDecl* R = new (C) RecordDecl(Record, TK, DC, StartLoc, IdLoc, Id,
                                      PrevDecl);
+  R->MayHaveOutOfDateDef = C.getLangOpts().Modules;
+
   C.getTypeDeclType(R, PrevDecl);
   return R;
 }
 
 RecordDecl *RecordDecl::CreateDeserialized(const ASTContext &C, unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, sizeof(RecordDecl));
-  return new (Mem) RecordDecl(Record, TTK_Struct, 0, SourceLocation(),
-                              SourceLocation(), 0, 0);
+  RecordDecl *R = new (Mem) RecordDecl(Record, TTK_Struct, 0, SourceLocation(),
+                                       SourceLocation(), 0, 0);
+  R->MayHaveOutOfDateDef = C.getLangOpts().Modules;
+  return R;
 }
 
 bool RecordDecl::isInjectedClassName() const {
diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index e1202c2..2073658 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -40,6 +40,10 @@
 #define ABSTRACT_DECL(DECL)
 #include "clang/AST/DeclNodes.inc"
 
+void Decl::updateOutOfDate(IdentifierInfo &II) const {
+  getASTContext().getExternalSource()->updateOutOfDateIdentifier(II);
+}
+
 void *Decl::AllocateDeserializedDecl(const ASTContext &Context, 
                                      unsigned ID,
                                      unsigned Size) {
diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index 90a2b4a..4dd3694 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/lib/AST/DeclCXX.cpp
@@ -87,6 +87,7 @@
                                      bool DelayTypeCreation) {
   CXXRecordDecl* R = new (C) CXXRecordDecl(CXXRecord, TK, DC, StartLoc, IdLoc,
                                            Id, PrevDecl);
+  R->MayHaveOutOfDateDef = C.getLangOpts().Modules;
 
   // FIXME: DelayTypeCreation seems like such a hack
   if (!DelayTypeCreation)
@@ -101,6 +102,7 @@
                                            0, 0);
   R->IsBeingDefined = true;
   R->DefinitionData = new (C) struct LambdaDefinitionData(R, Info, Dependent);
+  R->MayHaveOutOfDateDef = false;
   C.getTypeDeclType(R, /*PrevDecl=*/0);
   return R;
 }
@@ -108,8 +110,11 @@
 CXXRecordDecl *
 CXXRecordDecl::CreateDeserialized(const ASTContext &C, unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, sizeof(CXXRecordDecl));
-  return new (Mem) CXXRecordDecl(CXXRecord, TTK_Struct, 0, SourceLocation(),
-                                 SourceLocation(), 0, 0);
+  CXXRecordDecl *R = new (Mem) CXXRecordDecl(CXXRecord, TTK_Struct, 0,
+                                             SourceLocation(), SourceLocation(),
+                                             0, 0);
+  R->MayHaveOutOfDateDef = false;
+  return R;
 }
 
 void
diff --git a/lib/AST/DeclObjC.cpp b/lib/AST/DeclObjC.cpp
index b99c45c..ce765a7 100644
--- a/lib/AST/DeclObjC.cpp
+++ b/lib/AST/DeclObjC.cpp
@@ -301,8 +301,8 @@
 
 void ObjCInterfaceDecl::allocateDefinitionData() {
   assert(!hasDefinition() && "ObjC class already has a definition");
-  Data = new (getASTContext()) DefinitionData();
-  Data->Definition = this;
+  Data.setPointer(new (getASTContext()) DefinitionData());
+  Data.getPointer()->Definition = this;
 
   // Make the type point at the definition, now that we have one.
   if (TypeForDecl)
@@ -1011,6 +1011,7 @@
                                              bool isInternal){
   ObjCInterfaceDecl *Result = new (C) ObjCInterfaceDecl(DC, atLoc, Id, ClassLoc, 
                                                         PrevDecl, isInternal);
+  Result->Data.setInt(!C.getLangOpts().Modules);
   C.getObjCInterfaceType(Result, PrevDecl);
   return Result;
 }
@@ -1018,8 +1019,11 @@
 ObjCInterfaceDecl *ObjCInterfaceDecl::CreateDeserialized(ASTContext &C, 
                                                          unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, sizeof(ObjCInterfaceDecl));
-  return new (Mem) ObjCInterfaceDecl(0, SourceLocation(), 0, SourceLocation(),
-                                     0, false);
+  ObjCInterfaceDecl *Result = new (Mem) ObjCInterfaceDecl(0, SourceLocation(),
+                                                          0, SourceLocation(),
+                                                          0, false);
+  Result->Data.setInt(!C.getLangOpts().Modules);
+  return Result;
 }
 
 ObjCInterfaceDecl::
@@ -1334,15 +1338,17 @@
                                            ObjCProtocolDecl *PrevDecl) {
   ObjCProtocolDecl *Result 
     = new (C) ObjCProtocolDecl(DC, Id, nameLoc, atStartLoc, PrevDecl);
-  
+  Result->Data.setInt(!C.getLangOpts().Modules);
   return Result;
 }
 
 ObjCProtocolDecl *ObjCProtocolDecl::CreateDeserialized(ASTContext &C, 
                                                        unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, sizeof(ObjCProtocolDecl));
-  return new (Mem) ObjCProtocolDecl(0, 0, SourceLocation(), SourceLocation(),
-                                    0);
+  ObjCProtocolDecl *Result = new (Mem) ObjCProtocolDecl(0, 0, SourceLocation(),
+                                                        SourceLocation(), 0);
+  Result->Data.setInt(!C.getLangOpts().Modules);
+  return Result;
 }
 
 ObjCProtocolDecl *ObjCProtocolDecl::lookupProtocolNamed(IdentifierInfo *Name) {
@@ -1380,9 +1386,9 @@
 }
 
 void ObjCProtocolDecl::allocateDefinitionData() {
-  assert(!Data && "Protocol already has a definition!");
-  Data = new (getASTContext()) DefinitionData;
-  Data->Definition = this;
+  assert(!Data.getPointer() && "Protocol already has a definition!");
+  Data.setPointer(new (getASTContext()) DefinitionData);
+  Data.getPointer()->Definition = this;
 }
 
 void ObjCProtocolDecl::startDefinition() {
diff --git a/lib/AST/DeclTemplate.cpp b/lib/AST/DeclTemplate.cpp
index bd5ab8a..42929aa 100644
--- a/lib/AST/DeclTemplate.cpp
+++ b/lib/AST/DeclTemplate.cpp
@@ -728,6 +728,8 @@
                                                    SpecializedTemplate,
                                                    Args, NumArgs,
                                                    PrevDecl);
+  Result->MayHaveOutOfDateDef = false;
+
   Context.getTypeDeclType(Result, PrevDecl);
   return Result;
 }
@@ -737,7 +739,10 @@
                                                     unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, 
                                        sizeof(ClassTemplateSpecializationDecl));
-  return new (Mem) ClassTemplateSpecializationDecl(ClassTemplateSpecialization);
+  ClassTemplateSpecializationDecl *Result =
+    new (Mem) ClassTemplateSpecializationDecl(ClassTemplateSpecialization);
+  Result->MayHaveOutOfDateDef = false;
+  return Result;
 }
 
 void
@@ -857,6 +862,7 @@
                                                           PrevDecl,
                                                           SequenceNumber);
   Result->setSpecializationKind(TSK_ExplicitSpecialization);
+  Result->MayHaveOutOfDateDef = false;
 
   Context.getInjectedClassNameType(Result, CanonInjectedType);
   return Result;
@@ -867,7 +873,10 @@
                                                            unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, 
                 sizeof(ClassTemplatePartialSpecializationDecl));
-  return new (Mem) ClassTemplatePartialSpecializationDecl();
+  ClassTemplatePartialSpecializationDecl *Result
+    = new (Mem) ClassTemplatePartialSpecializationDecl();
+  Result->MayHaveOutOfDateDef = false;
+  return Result;
 }
 
 //===----------------------------------------------------------------------===//