diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index 9a61e34..08e706c 100644
--- a/lib/CodeGen/CGObjCMac.cpp
+++ b/lib/CodeGen/CGObjCMac.cpp
@@ -433,19 +433,19 @@
   
   /// SyncEnterFn - LLVM object_sync_enter function.
   llvm::Constant *getSyncEnterFn() {
-    // void objc_sync_enter (id)
+    // int objc_sync_enter (id)
     llvm::Type *args[] = { ObjectPtrTy };
     llvm::FunctionType *FTy =
-      llvm::FunctionType::get(CGM.VoidTy, args, false);
+      llvm::FunctionType::get(CGM.IntTy, args, false);
     return CGM.CreateRuntimeFunction(FTy, "objc_sync_enter");
   }
 
   /// SyncExitFn - LLVM object_sync_exit function.
   llvm::Constant *getSyncExitFn() {
-    // void objc_sync_exit (id)
+    // int objc_sync_exit (id)
     llvm::Type *args[] = { ObjectPtrTy };
     llvm::FunctionType *FTy =
-      llvm::FunctionType::get(CGM.VoidTy, args, false);
+      llvm::FunctionType::get(CGM.IntTy, args, false);
     return CGM.CreateRuntimeFunction(FTy, "objc_sync_exit");
   }
 
diff --git a/lib/Rewrite/Frontend/RewriteModernObjC.cpp b/lib/Rewrite/Frontend/RewriteModernObjC.cpp
index c735da0..0dbdbae 100644
--- a/lib/Rewrite/Frontend/RewriteModernObjC.cpp
+++ b/lib/Rewrite/Frontend/RewriteModernObjC.cpp
@@ -5891,8 +5891,8 @@
   Preamble += "(const char *);\n";
   Preamble += "__OBJC_RW_DLLIMPORT void objc_exception_throw( struct objc_object *);\n";
   // @synchronized hooks.
-  Preamble += "__OBJC_RW_DLLIMPORT void objc_sync_enter( struct objc_object *);\n";
-  Preamble += "__OBJC_RW_DLLIMPORT void objc_sync_exit( struct objc_object *);\n";
+  Preamble += "__OBJC_RW_DLLIMPORT int objc_sync_enter( struct objc_object *);\n";
+  Preamble += "__OBJC_RW_DLLIMPORT int objc_sync_exit( struct objc_object *);\n";
   Preamble += "__OBJC_RW_DLLIMPORT Protocol *objc_getProtocol(const char *);\n";
   Preamble += "#ifndef __FASTENUMERATIONSTATE\n";
   Preamble += "struct __objcFastEnumerationState {\n\t";
diff --git a/lib/Rewrite/Frontend/RewriteObjC.cpp b/lib/Rewrite/Frontend/RewriteObjC.cpp
index 0b9e656..5a0ac54 100644
--- a/lib/Rewrite/Frontend/RewriteObjC.cpp
+++ b/lib/Rewrite/Frontend/RewriteObjC.cpp
@@ -5112,8 +5112,8 @@
   Preamble += "__OBJC_RW_DLLIMPORT int objc_exception_match";
   Preamble += "(struct objc_class *, struct objc_object *);\n";
   // @synchronized hooks.
-  Preamble += "__OBJC_RW_DLLIMPORT void objc_sync_enter(struct objc_object *);\n";
-  Preamble += "__OBJC_RW_DLLIMPORT void objc_sync_exit(struct objc_object *);\n";
+  Preamble += "__OBJC_RW_DLLIMPORT int objc_sync_enter(struct objc_object *);\n";
+  Preamble += "__OBJC_RW_DLLIMPORT int objc_sync_exit(struct objc_object *);\n";
   Preamble += "__OBJC_RW_DLLIMPORT Protocol *objc_getProtocol(const char *);\n";
   Preamble += "#ifndef __FASTENUMERATIONSTATE\n";
   Preamble += "struct __objcFastEnumerationState {\n\t";