diff --git a/include/clang/Serialization/ASTReader.h b/include/clang/Serialization/ASTReader.h
index 51db35e..e87c93f 100644
--- a/include/clang/Serialization/ASTReader.h
+++ b/include/clang/Serialization/ASTReader.h
@@ -687,7 +687,7 @@
   /// Objective-C protocols.
   std::deque<Decl *> InterestingDecls;
 
-  /// \brief The set of redeclarable declaraations that have been deserialized
+  /// \brief The set of redeclarable declarations that have been deserialized
   /// since the last time the declaration chains were linked.
   llvm::SmallPtrSet<Decl *, 16> RedeclsDeserialized;
   
@@ -854,6 +854,10 @@
 
   void finishPendingActions();
 
+  /// \brief Whether D needs to be instantiated, i.e. whether an instantiation
+  /// for D does not exist yet.
+  bool needPendingInstantiation(ValueDecl* D) const;
+
   /// \brief Produce an error diagnostic and return true.
   ///
   /// This routine should only be used for fatal errors that have to
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 639ef93..a897d86 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -2223,13 +2223,15 @@
 
     case PENDING_IMPLICIT_INSTANTIATIONS:
       if (PendingInstantiations.size() % 2 != 0) {
+        Error("Invalid existing PendingInstantiations");
+        return Failure;
+      }
+
+      if (Record.size() % 2 != 0) {
         Error("Invalid PENDING_IMPLICIT_INSTANTIATIONS block");
         return Failure;
       }
-        
-      // Later lists of pending instantiations overwrite earlier ones.
-      // FIXME: This is most certainly wrong for modules.
-      PendingInstantiations.clear();
+
       for (unsigned I = 0, N = Record.size(); I != N; /* in loop */) {
         PendingInstantiations.push_back(getGlobalDeclID(F, Record[I++]));
         PendingInstantiations.push_back(
@@ -5592,7 +5594,11 @@
     ValueDecl *D = cast<ValueDecl>(GetDecl(PendingInstantiations[Idx++]));
     SourceLocation Loc
       = SourceLocation::getFromRawEncoding(PendingInstantiations[Idx++]);
-    Pending.push_back(std::make_pair(D, Loc));
+
+    // For modules, find out whether an instantiation already exists
+    if (!getContext().getLangOpts().Modules
+        || needPendingInstantiation(D))
+      Pending.push_back(std::make_pair(D, Loc));
   }  
   PendingInstantiations.clear();
 }
diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index fb4192f..85740de 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -2156,7 +2156,7 @@
   // loading, and some declarations may still be initializing.
   if (isConsumerInterestedIn(D))
     InterestingDecls.push_back(D);
-  
+
   return D;
 }
 
@@ -2504,3 +2504,60 @@
     }
   }
 }
+
+/// \brief Return a template specialization of ND (should be a TemplateDecl)
+///  that matches FD or TD.
+static NamedDecl* findMatchingSpecialization(FunctionDecl* FD,
+                                             ClassTemplateSpecializationDecl*TD,
+                                             NamedDecl* ND) {
+  TemplateDecl* Templt = dyn_cast<TemplateDecl>(ND);
+  if (!Templt) return 0;
+  if (FD) {
+    FunctionTemplateDecl* FTD = dyn_cast<FunctionTemplateDecl>(Templt);
+    if (!FTD) return 0;
+    const TemplateArgumentList* TmpltArgs = FD->getTemplateSpecializationArgs();
+    assert(TmpltArgs || "Template without arguments");
+    void* InsertionPoint;
+    return FTD->findSpecialization(TmpltArgs->data(), TmpltArgs->size(),
+                                   InsertionPoint);
+  } else {
+    ClassTemplateDecl* CTD = dyn_cast<ClassTemplateDecl>(Templt);
+    if (!CTD) return 0;
+    const TemplateArgumentList& TmpltArgs = TD->getTemplateArgs();
+    void* InsertionPoint;
+    return CTD->findSpecialization(TmpltArgs.data(), TmpltArgs.size(),
+                                   InsertionPoint);
+  }
+  return 0;
+}
+
+/// \brief Find out whether an instantiation (outside the module) already exists
+bool ASTReader::needPendingInstantiation(ValueDecl* D) const {
+  DeclContext *DC = D->getDeclContext()->getRedeclContext();
+  DeclarationName Name = D->getDeclName();
+  assert(Name && "unnamed template");
+
+  FunctionDecl* FD = dyn_cast<FunctionDecl>(D);
+  ClassTemplateSpecializationDecl* CD
+    = FD ? 0 : dyn_cast<ClassTemplateSpecializationDecl>(D);
+
+  NamedDecl* FoundSpecialization = 0;
+  if (DC->isTranslationUnit() && SemaObj) {
+    IdentifierResolver &IdResolver = SemaObj->IdResolver;
+    for (IdentifierResolver::iterator I = IdResolver.begin(Name), 
+           IEnd = IdResolver.end();
+         I != IEnd && !FoundSpecialization; ++I)
+      FoundSpecialization = findMatchingSpecialization(FD, CD, *I);
+  } else {
+    // templates are redeclarables, i.e. they must have been merged into
+    // the primary context. Use localUncachedLookup to not pick up template
+    // decls from modules again.
+    llvm::SmallVector<NamedDecl*, 6> Results;
+    DC->getPrimaryContext()->localUncachedLookup(Name, Results);
+    for (llvm::SmallVector<NamedDecl *, 6>::const_iterator
+           I = Results.begin(), E = Results.end();
+         I != E && FoundSpecialization; ++I)
+      FoundSpecialization = findMatchingSpecialization(FD, CD, *I);
+  }
+  return FoundSpecialization && isSameEntity(FoundSpecialization, D);
+}
diff --git a/test/Modules/Inputs/module.map b/test/Modules/Inputs/module.map
index 79056cb..9044922 100644
--- a/test/Modules/Inputs/module.map
+++ b/test/Modules/Inputs/module.map
@@ -78,6 +78,18 @@
   header "namespaces-right.h"
   export *
 }
+module templates_top { 
+  header "templates-top.h"
+  export *
+}
+module templates_left { 
+  header "templates-left.h"
+  export *
+}
+module templates_right { 
+  header "templates-right.h"
+  export *
+}
 module MethodPoolA {
   header "MethodPoolA.h"
 }
diff --git a/test/Modules/Inputs/redecl-merge-bottom.h b/test/Modules/Inputs/redecl-merge-bottom.h
index 40a9404..cfea7dc 100644
--- a/test/Modules/Inputs/redecl-merge-bottom.h
+++ b/test/Modules/Inputs/redecl-merge-bottom.h
@@ -18,11 +18,3 @@
 
 void refers_to_C4(C4*);
 
-#ifdef __cplusplus
-template<typename T> class Vector;
-
-template<typename T> class Vector;
-
-template<typename T> class Vector;
-#endif
-
diff --git a/test/Modules/Inputs/redecl-merge-left.h b/test/Modules/Inputs/redecl-merge-left.h
index 1f5da4f..ee794ff 100644
--- a/test/Modules/Inputs/redecl-merge-left.h
+++ b/test/Modules/Inputs/redecl-merge-left.h
@@ -78,27 +78,6 @@
 
 extern double var3;
 
-#ifdef __cplusplus
-template<typename T> class Vector;
-
-template<typename T> class Vector;
-
-template<typename T> class List;
-template<> class List<bool> {
-public:
-  void push_back(int);
-};
-namespace N {
-  template<typename T> class Set;
-}
-namespace N {
-  template<typename T> class Set {
-  public:
-    void insert(T);
-  };
-}
-#endif
-
 // Make sure this doesn't introduce an ambiguity-creating 'id' at the
 // top level.
 typedef void funcptr_with_id(int id);
diff --git a/test/Modules/Inputs/redecl-merge-right.h b/test/Modules/Inputs/redecl-merge-right.h
index 2e05c03..f62020f 100644
--- a/test/Modules/Inputs/redecl-merge-right.h
+++ b/test/Modules/Inputs/redecl-merge-right.h
@@ -78,26 +78,6 @@
 
 static double var3;
 
-#ifdef __cplusplus
-template<typename T> class Vector { 
-public:
-  void push_back(const T&);
-};
-
-template<typename T> class List;
-template<> class List<bool> {
-public:
-  void push_back(int);
-};
-
-namespace N {
-  template<typename T> class Set {
-  public:
-    void insert(T);
-  };
-}
-#endif
-
 int ONE;
 @__experimental_modules_import redecl_merge_top.Explicit;
 const int one = ONE;
diff --git a/test/Modules/Inputs/redecl-merge-top.h b/test/Modules/Inputs/redecl-merge-top.h
index 7053936..25456de 100644
--- a/test/Modules/Inputs/redecl-merge-top.h
+++ b/test/Modules/Inputs/redecl-merge-top.h
@@ -14,12 +14,3 @@
 struct S1;
 struct S2;
 struct S2;
-
-#ifdef __cplusplus
-template<typename T> class Vector;
-
-template<typename T> class List {
-public:
-  void push_back(T);
-};
-#endif
diff --git a/test/Modules/Inputs/templates-left.h b/test/Modules/Inputs/templates-left.h
new file mode 100644
index 0000000..7f50cd4
--- /dev/null
+++ b/test/Modules/Inputs/templates-left.h
@@ -0,0 +1,27 @@
+@__experimental_modules_import templates_top;
+
+template<typename T> class Vector;
+
+template<typename T> class Vector;
+
+template<typename T> class List;
+template<> class List<bool> {
+public:
+  void push_back(int);
+};
+namespace N {
+  template<typename T> class Set;
+}
+namespace N {
+  template<typename T> class Set {
+  public:
+    void insert(T);
+  };
+}
+
+template <typename T>
+void pendingInstantiation(T) {}
+void triggerPendingInstantiation() {
+  pendingInstantiation(12);
+  pendingInstantiation(42.);
+}
diff --git a/test/Modules/Inputs/templates-right.h b/test/Modules/Inputs/templates-right.h
new file mode 100644
index 0000000..f5487fb
--- /dev/null
+++ b/test/Modules/Inputs/templates-right.h
@@ -0,0 +1,25 @@
+@__experimental_modules_import templates_top;
+
+template<typename T> class Vector { 
+public:
+  void push_back(const T&);
+};
+
+template<typename T> class List;
+template<> class List<bool> {
+public:
+  void push_back(int);
+};
+
+namespace N {
+  template<typename T> class Set {
+  public:
+    void insert(T);
+  };
+}
+
+template <typename T>
+void pendingInstantiation(T) {}
+void triggerPendingInstantiationToo() {
+  pendingInstantiation(12);
+}
diff --git a/test/Modules/Inputs/templates-top.h b/test/Modules/Inputs/templates-top.h
new file mode 100644
index 0000000..80ecf23
--- /dev/null
+++ b/test/Modules/Inputs/templates-top.h
@@ -0,0 +1,6 @@
+template<typename T> class Vector;
+
+template<typename T> class List {
+public:
+  void push_back(T);
+};
diff --git a/test/Modules/redecl-merge.m b/test/Modules/redecl-merge.m
index 96b0b47..d722414 100644
--- a/test/Modules/redecl-merge.m
+++ b/test/Modules/redecl-merge.m
@@ -1,6 +1,5 @@
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -fmodules -fmodule-cache-path %t -I %S/Inputs %s -verify -Wno-objc-root-class
-// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodule-cache-path %t -I %S/Inputs %s -verify -Wno-objc-root-class
 @class C2;
 @class C3;
 @class C3;
@@ -57,26 +56,26 @@
 
 void testTypedefMerge(int i, double d) {
   T1 *ip = &i;
-  // in other file: expected-note{{candidate found by name lookup is 'T2'}}
   // FIXME: Typedefs aren't actually merged in the sense of other merges, because
   // we should only merge them when the types are identical.
-  // in other file: expected-note{{candidate found by name lookup is 'T2'}}
-  // in other file: expected-note{{candidate function}}
+  // in other file: expected-note@60{{candidate found by name lookup is 'T2'}}
+  // in other file: expected-note@63{{candidate found by name lookup is 'T2'}}
   T2 *dp = &d; // expected-error{{reference to 'T2' is ambiguous}}
 }
 
 void testFuncMerge(int i) {
   func0(i);
-  // in other file: expected-note{{candidate function}}
   func1(i);
+  // in other file: expected-note@64{{candidate function}}
+  // in other file: expected-note@70{{candidate function}}
   func2(i); // expected-error{{call to 'func2' is ambiguous}}
 }
 
 void testVarMerge(int i) {
   var1 = i;
-  // in other files: expected-note 2{{candidate found by name lookup is 'var2'}}
+  // in other files: expected-note@77 2{{candidate found by name lookup is 'var2'}}
   var2 = i; // expected-error{{reference to 'var2' is ambiguous}}
-  // in other files: expected-note 2{{candidate found by name lookup is 'var3'}}
+  // in other files: expected-note@79 2{{candidate found by name lookup is 'var3'}}
   var3 = i; // expected-error{{reference to 'var3' is ambiguous}}
 }
 
@@ -146,19 +145,6 @@
 id<P4> p4;
 id<P3> p3;
 
-#ifdef __cplusplus
-void testVector() {
-  Vector<int> vec_int;
-  vec_int.push_back(0);
-
-  List<bool> list_bool;
-  list_bool.push_back(false);
-
-  N::Set<char> set_char;
-  set_char.insert('A');
-}
-#endif
-
 // Make sure we don't get conflicts with 'id'.
 funcptr_with_id fid;
 id id_global;
diff --git a/test/Modules/templates.mm b/test/Modules/templates.mm
new file mode 100644
index 0000000..a9b4591
--- /dev/null
+++ b/test/Modules/templates.mm
@@ -0,0 +1,28 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodule-cache-path %t -I %S/Inputs -verify %s -Wno-objc-root-class
+// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodule-cache-path %t -I %S/Inputs -emit-llvm %s -o - -Wno-objc-root-class | grep pendingInstantiation | FileCheck %s
+
+@__experimental_modules_import templates_left;
+@__experimental_modules_import templates_right;
+
+
+void testTemplateClasses() {
+  Vector<int> vec_int;
+  vec_int.push_back(0);
+
+  List<bool> list_bool;
+  list_bool.push_back(false);
+
+  N::Set<char> set_char;
+  set_char.insert('A');
+}
+
+void testPendingInstantiations() {
+  // CHECK: call
+  // CHECK: call
+  // CHECK: {{define .*pendingInstantiation.*[(]i}}
+  // CHECK: {{define .*pendingInstantiation.*[(]double}}
+  // CHECK: call
+  triggerPendingInstantiation();
+  triggerPendingInstantiationToo();
+}