diff --git a/include/clang/Basic/DiagnosticKinds.def b/include/clang/Basic/DiagnosticKinds.def
index cf4bf2a..84aa391 100644
--- a/include/clang/Basic/DiagnosticKinds.def
+++ b/include/clang/Basic/DiagnosticKinds.def
@@ -467,6 +467,12 @@
      "method definition for '%0' not found")
 DIAG(warn_incomplete_impl, WARNING,
      "incomplete implementation")
+DIAG(warn_multiple_method_decl, WARNING,
+     "multiple methods named '%0' found")
+DIAG(warn_using_decl, WARNING,
+     "using")
+DIAG(warn_also_found_decl, WARNING,
+     "also found")
 DIAG(error_duplicate_method_decl, ERROR,
      "duplicate declaration of method '%0'")
 DIAG(err_previous_declaration, ERROR,
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index dcd197d..49d69ad 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -379,6 +379,10 @@
   /// messages sent to "id" (where the class of the object is unknown).
   void AddInstanceMethodToGlobalPool(ObjCMethodDecl *Method);
   
+  /// LookupInstanceMethodInGlobalPool - Returns the method and warns if
+  /// there are multiple signatures.
+  ObjCMethodDecl *LookupInstanceMethodInGlobalPool(Selector Sel, SourceRange R);
+  
   /// AddFactoryMethodToGlobalPool - Same as above, but for factory methods.
   void AddFactoryMethodToGlobalPool(ObjCMethodDecl *Method);
   //===--------------------------------------------------------------------===//
diff --git a/lib/Sema/SemaDeclObjC.cpp b/lib/Sema/SemaDeclObjC.cpp
index f98eeb6..05c3bc7 100644
--- a/lib/Sema/SemaDeclObjC.cpp
+++ b/lib/Sema/SemaDeclObjC.cpp
@@ -776,6 +776,21 @@
   }
 }
 
+ObjCMethodDecl *Sema::LookupInstanceMethodInGlobalPool(Selector Sel, 
+                                                       SourceRange R) {
+  ObjCMethodList &MethList = InstanceMethodPool[Sel];
+  
+  if (MethList.Method && MethList.Next) {
+    Diag(R.getBegin(), diag::warn_multiple_method_decl, Sel.getName(), R);
+    Diag(MethList.Method->getLocStart(), diag::warn_using_decl, 
+         MethList.Method->getSourceRange());
+    for (ObjCMethodList *Next = MethList.Next; Next; Next = Next->Next)
+      Diag(Next->Method->getLocStart(), diag::warn_also_found_decl, 
+           Next->Method->getSourceRange());
+  }
+  return MethList.Method;
+}
+
 void Sema::AddFactoryMethodToGlobalPool(ObjCMethodDecl *Method) {
   ObjCMethodList &FirstMethod = FactoryMethodPool[Method->getSelector()];
   if (!FirstMethod.Method) {
diff --git a/lib/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index db83405..a474b7e 100644
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -283,7 +283,8 @@
   // Handle messages to id.
   if (ReceiverCType == Context.getCanonicalType(Context.getObjCIdType()) ||
       ReceiverCType->getAsBlockPointerType()) {
-    ObjCMethodDecl *Method = InstanceMethodPool[Sel].Method;
+    ObjCMethodDecl *Method = LookupInstanceMethodInGlobalPool(
+                               Sel, SourceRange(lbrac,rbrac));
     if (!Method)
       Method = FactoryMethodPool[Sel].Method;
     if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, "-", 
@@ -306,7 +307,8 @@
     if (!Method)
       Method = FactoryMethodPool[Sel].Method;
     if (!Method)
-      Method = InstanceMethodPool[Sel].Method;
+      Method = LookupInstanceMethodInGlobalPool(
+                               Sel, SourceRange(lbrac,rbrac));
     if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, "-", 
                                   lbrac, rbrac, returnType))
       return true;
@@ -335,9 +337,9 @@
     // We allow sending a message to a pointer to an interface (an object).
     
     ClassDecl = OCIReceiver->getDecl();
-    // FIXME: consider using InstanceMethodPool, since it will be faster
-    // than the following method (which can do *many* linear searches). The
-    // idea is to add class info to InstanceMethodPool.
+    // FIXME: consider using LookupInstanceMethodInGlobalPool, since it will be
+    // faster than the following method (which can do *many* linear searches). 
+    // The idea is to add class info to InstanceMethodPool.
     Method = ClassDecl->lookupInstanceMethod(Sel);
     
     if (!Method) {
@@ -369,7 +371,8 @@
         // behavior isn't very desirable, however we need it for GCC
         // compatibility.
         if (!Method)
-          Method = InstanceMethodPool[Sel].Method;
+          Method = LookupInstanceMethodInGlobalPool(
+                               Sel, SourceRange(lbrac,rbrac));
   }
   if (CheckMessageArgumentTypes(ArgExprs, NumArgs, Sel, Method, "-", 
                                 lbrac, rbrac, returnType))
diff --git a/test/SemaObjC/method-lookup-3.m b/test/SemaObjC/method-lookup-3.m
new file mode 100644
index 0000000..a1815fa
--- /dev/null
+++ b/test/SemaObjC/method-lookup-3.m
@@ -0,0 +1,52 @@
+// RUN: clang -fsyntax-only -verify %s
+
+typedef struct { int y; } Abstract;
+
+typedef struct { int x; } Alternate;
+
+#define INTERFERE_TYPE Alternate*
+
+@protocol A
+@property Abstract *x; // expected-warning{{using}}
+@end
+
+@interface B
+@property Abstract *y; // expected-warning{{using}}
+@end
+
+@interface B (Category)
+@property Abstract *z; // expected-warning{{using}}
+@end
+
+@interface InterferencePre
+-(void) x; // expected-warning{{also found}}
+-(void) y; // expected-warning{{also found}}
+-(void) z; // expected-warning{{also found}}
+-(void) setX: (INTERFERE_TYPE) arg; // expected-warning{{also found}}
+-(void) setY: (INTERFERE_TYPE) arg; // expected-warning{{also found}}
+-(void) setZ: (INTERFERE_TYPE) arg; // expected-warning{{also found}}
+@end
+
+void f0(id a0) {
+  Abstract *l = [a0 x]; // expected-warning {{multiple methods named 'x' found}} 
+}
+
+void f1(id a0) {
+  Abstract *l = [a0 y]; // expected-warning {{multiple methods named 'y' found}}
+}
+
+void f2(id a0) {
+  Abstract *l = [a0 z]; // expected-warning {{multiple methods named 'z' found}}
+}
+
+void f3(id a0, Abstract *a1) { 
+  [ a0 setX: a1]; // expected-warning {{multiple methods named 'setX:' found}}
+}
+
+void f4(id a0, Abstract *a1) { 
+  [ a0 setY: a1]; // expected-warning {{multiple methods named 'setY:' found}}
+}
+
+void f5(id a0, Abstract *a1) { 
+  [ a0 setZ: a1]; // expected-warning {{multiple methods named 'setZ:' found}}
+}