diff --git a/lib/CodeGen/MachOWriter.h b/lib/CodeGen/MachOWriter.h
index e5c7ee6c253..9d8e9d450ba 100644
--- a/lib/CodeGen/MachOWriter.h
+++ b/lib/CodeGen/MachOWriter.h
@@ -22,6 +22,7 @@ namespace llvm {
   class Constant;
   class GlobalVariable;
   class Mangler;
+  class MachineBasicBlock;
   class MachineRelocation;
   class MachOCodeEmitter;
   struct MachODySymTab;