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";