diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 4a7be55..003be82 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1397,7 +1397,9 @@
   // __module_private__ is propagated to later declarations.
   if (Old->isModulePrivate())
     New->setModulePrivate();
-    
+  else if (New->isModulePrivate())
+    diagnoseModulePrivateRedeclaration(New, Old);
+           
   if (getLangOptions().Microsoft)
     return;
 
@@ -1966,7 +1968,9 @@
   // __module_private__ is propagated to later declarations.
   if (Old->isModulePrivate())
     New->setModulePrivate();
-  
+  else if (New->isModulePrivate())
+    diagnoseModulePrivateRedeclaration(New, Old);
+
   // Merge attributes from the parameters.  These can mismatch with K&R
   // declarations.
   if (New->getNumParams() == Old->getNumParams())
@@ -2152,6 +2156,8 @@
   // __module_private__ is propagated to later declarations.
   if (Old->isModulePrivate())
     New->setModulePrivate();
+  else if (New->isModulePrivate())
+    diagnoseModulePrivateRedeclaration(New, Old);
 
   // Variables with external linkage are analyzed in FinalizeDeclaratorGroup.
 
@@ -7139,7 +7145,7 @@
                      SourceLocation KWLoc, CXXScopeSpec &SS,
                      IdentifierInfo *Name, SourceLocation NameLoc,
                      AttributeList *Attr, AccessSpecifier AS,
-                     bool IsModulePrivate,
+                     SourceLocation ModulePrivateLoc,
                      MultiTemplateParamsArg TemplateParameterLists,
                      bool &OwnedDecl, bool &IsDependent,
                      bool ScopedEnum, bool ScopedEnumUsesClassTag,
@@ -7179,7 +7185,7 @@
         DeclResult Result = CheckClassTemplate(S, TagSpec, TUK, KWLoc,
                                                SS, Name, NameLoc, Attr,
                                                TemplateParams, AS,
-                                               IsModulePrivate,
+                                               ModulePrivateLoc,
                                            TemplateParameterLists.size() - 1,
                  (TemplateParameterList**) TemplateParameterLists.release());
         return Result.get();
@@ -7744,9 +7750,13 @@
 
   if (PrevDecl && PrevDecl->isModulePrivate())
     New->setModulePrivate();
-  else if (IsModulePrivate)
-    New->setModulePrivate();
-
+  else if (ModulePrivateLoc.isValid()) {
+    if (PrevDecl && !PrevDecl->isModulePrivate())
+      diagnoseModulePrivateRedeclaration(New, PrevDecl, ModulePrivateLoc);
+    else
+      New->setModulePrivate();
+  }
+  
   // If this is a specialization of a member class (of a class template),
   // check the specialization.
   if (isExplicitSpecialization && CheckMemberSpecialization(New, Previous))
@@ -9417,6 +9427,20 @@
   return DeclResult((Decl *)0);
 }
 
+void 
+Sema::diagnoseModulePrivateRedeclaration(NamedDecl *New, NamedDecl *Old,
+                                         SourceLocation ModulePrivateKeyword) {
+  assert(!Old->isModulePrivate() && "Old is module-private!");
+  
+  Diag(New->getLocation(), diag::err_module_private_follows_public)
+    << New->getDeclName() << SourceRange(ModulePrivateKeyword);
+  Diag(Old->getLocation(), diag::note_previous_declaration)
+    << Old->getDeclName();
+  
+  // Drop the __module_private__ from the new declaration, since it's invalid.
+  New->setModulePrivate(false);
+}
+
 void Sema::ActOnPragmaWeakID(IdentifierInfo* Name,
                              SourceLocation PragmaLoc,
                              SourceLocation NameLoc) {