diff --git a/include/llvm/Type.h b/include/llvm/Type.h
index dd2fd9b1132..d1ca0130d02 100644
--- a/include/llvm/Type.h
+++ b/include/llvm/Type.h
@@ -83,7 +83,7 @@ public:
 
 private:
   TypeID   ID : 8;    // The current base type of this type.
-  bool     Abstract;  // True if type contains an OpaqueType
+  bool     Abstract : 1;  // True if type contains an OpaqueType
 
   /// RefCount - This counts the number of PATypeHolders that are pointing to
   /// this type.  When this number falls to zero, if the type is abstract and