diff --git a/include/clang/AST/ASTContext.h b/include/clang/AST/ASTContext.h
index 46330a400f..5a04843054 100644
--- a/include/clang/AST/ASTContext.h
+++ b/include/clang/AST/ASTContext.h
@@ -1614,6 +1614,11 @@ public:
                                   const ObjCMethodDecl *Redecl) {
     ObjCMethodRedecls[MD] = Redecl;
   }
+
+  /// \brief Returns the objc interface that \arg ND belongs to if it is a
+  /// objc method/property/ivar etc. that is part of an interface,
+  /// otherwise returns null.
+  ObjCInterfaceDecl *getObjContainingInterface(NamedDecl *ND) const;
   
   /// \brief Set the copy inialization expression of a block var decl.
   void setBlockVarCopyInits(VarDecl*VD, Expr* Init);
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index b695a5b709..896a80a90f 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -1261,6 +1261,17 @@ void ASTContext::setObjCImplementation(ObjCCategoryDecl *CatD,
   ObjCImpls[CatD] = ImplD;
 }
 
+ObjCInterfaceDecl *ASTContext::getObjContainingInterface(NamedDecl *ND) const {
+  if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(ND->getDeclContext()))
+    return ID;
+  if (ObjCCategoryDecl *CD = dyn_cast<ObjCCategoryDecl>(ND->getDeclContext()))
+    return CD->getClassInterface();
+  if (ObjCImplDecl *IMD = dyn_cast<ObjCImplDecl>(ND->getDeclContext()))
+    return IMD->getClassInterface();
+
+  return 0;
+}
+
 /// \brief Get the copy initialization expression of VarDecl,or NULL if 
 /// none exists.
 Expr *ASTContext::getBlockVarCopyInits(const VarDecl*VD) {
diff --git a/test/Index/usrs.m b/test/Index/usrs.m
index a76394b746..e7a926f3f3 100644
--- a/test/Index/usrs.m
+++ b/test/Index/usrs.m
@@ -80,6 +80,14 @@ int test_multi_declaration(void) {
 - (void)method;
 @end
 
+@interface CWithExt2
+@end
+@interface CWithExt2 () {
+  id var_ext;
+}
+@property (assign) id pro_ext;
+@end
+
 // CHECK: usrs.m c:usrs.m@67@F@my_helper Extent=[3:1 - 3:60]
 // CHECK: usrs.m c:usrs.m@95@F@my_helper@x Extent=[3:29 - 3:34]
 // CHECK: usrs.m c:usrs.m@102@F@my_helper@y Extent=[3:36 - 3:41]
@@ -118,9 +126,9 @@ int test_multi_declaration(void) {
 // CHECK: usrs.m c:usrs.m@551@F@local_func@x Extent=[49:23 - 49:28]
 // CHECK: usrs.m c:objc(cs)CWithExt Extent=[51:1 - 53:5]
 // CHECK: usrs.m c:objc(cs)CWithExt(im)meth1 Extent=[52:1 - 52:14]
-// CHECK: usrs.m c:objc(cs)CWithExt Extent=[54:1 - 56:5]
+// CHECK: usrs.m c:objc(ext)CWithExt@usrs.m@612 Extent=[54:1 - 56:5]
 // CHECK: usrs.m c:objc(cs)CWithExt(im)meth2 Extent=[55:1 - 55:14]
-// CHECK: usrs.m c:objc(cs)CWithExt Extent=[57:1 - 59:5]
+// CHECK: usrs.m c:objc(ext)CWithExt@usrs.m@654 Extent=[57:1 - 59:5]
 // CHECK: usrs.m c:objc(cs)CWithExt(im)meth3 Extent=[58:1 - 58:14]
 // CHECK: usrs.m c:objc(cy)CWithExt@Bar Extent=[60:1 - 62:5]
 // CHECK: usrs.m c:objc(cs)CWithExt(im)meth4 Extent=[61:1 - 61:14]
@@ -137,6 +145,12 @@ int test_multi_declaration(void) {
 // CHECK: usrs.m c:usrs.m@980@F@test_multi_declaration@baz Extent=[74:25 - 74:32]
 // CHECK: usrs.m c:objc(pl)P1 Extent=[79:1 - 81:5]
 // CHECK: usrs.m c:objc(pl)P1(im)method Extent=[80:1 - 80:16]
+// CHECK: usrs.m c:objc(cs)CWithExt2 Extent=[83:1 - 84:5]
+// CHECK: usrs.m c:objc(ext)CWithExt2@usrs.m@1111 Extent=[85:1 - 89:5]
+// CHECK: usrs.m c:objc(cs)CWithExt2@var_ext Extent=[86:3 - 86:13]
+// CHECK: usrs.m c:objc(cs)CWithExt2(py)pro_ext Extent=[88:1 - 88:30]
+// CHECK: usrs.m c:objc(cs)CWithExt2(im)pro_ext Extent=[88:23 - 88:30]
+// CHECK: usrs.m c:objc(cs)CWithExt2(im)setPro_ext: Extent=[88:23 - 88:30]
 
 // RUN: c-index-test -test-load-source all %s | FileCheck -check-prefix=CHECK-source %s
 // CHECK-source: usrs.m:3:19: FunctionDecl=my_helper:3:19 (Definition) Extent=[3:1 - 3:60]
diff --git a/tools/libclang/CIndexUSRs.cpp b/tools/libclang/CIndexUSRs.cpp
index 11b124c562..32c4db6abe 100644
--- a/tools/libclang/CIndexUSRs.cpp
+++ b/tools/libclang/CIndexUSRs.cpp
@@ -169,7 +169,12 @@ void USRGenerator::VisitDeclContext(DeclContext *DC) {
 }
 
 void USRGenerator::VisitFieldDecl(FieldDecl *D) {
-  VisitDeclContext(D->getDeclContext());
+  // The USR for an ivar declared in a class extension is based on the
+  // ObjCInterfaceDecl, not the ObjCCategoryDecl.
+  if (ObjCInterfaceDecl *ID = Context->getObjContainingInterface(D))
+    Visit(ID);
+  else
+    VisitDeclContext(D->getDeclContext());
   Out << (isa<ObjCIvarDecl>(D) ? "@" : "@FI@");
   if (EmitDeclName(D)) {
     // Bit fields can be anonymous.
@@ -336,9 +341,11 @@ void USRGenerator::VisitObjCContainerDecl(ObjCContainerDecl *D) {
         IgnoreResults = true;
         return;
       }
+      // Specially handle class extensions, which are anonymous categories.
+      // We want to mangle in the location to uniquely distinguish them.
       if (CD->IsClassExtension()) {
-        // An extension semantically continues the interface of the class.
-        GenObjCClass(ID->getName());
+        Out << "objc(ext)" << ID->getName() << '@';
+        GenLoc(CD);
       }
       else
         GenObjCCategory(ID->getName(), CD->getName());
@@ -366,7 +373,12 @@ void USRGenerator::VisitObjCContainerDecl(ObjCContainerDecl *D) {
 }
 
 void USRGenerator::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
-  Visit(cast<Decl>(D->getDeclContext()));
+  // The USR for a property declared in a class extension or category is based
+  // on the ObjCInterfaceDecl, not the ObjCCategoryDecl.
+  if (ObjCInterfaceDecl *ID = Context->getObjContainingInterface(D))
+    Visit(ID);
+  else
+    Visit(cast<Decl>(D->getDeclContext()));
   GenObjCProperty(D->getName());
 }