diff --git a/clang/include/clang/AST/CXXInheritance.h b/clang/include/clang/AST/CXXInheritance.h
index eec2119f4a180..d18e1ce7e0e9e 100644
--- a/clang/include/clang/AST/CXXInheritance.h
+++ b/clang/include/clang/AST/CXXInheritance.h
@@ -131,6 +131,7 @@ class CXXBasePaths {
   /// class subobjects for that class type. The key of the map is
   /// the cv-unqualified canonical type of the base class subobject.
   struct IsVirtBaseAndNumberNonVirtBases {
+    LLVM_PREFERRED_TYPE(bool)
     unsigned IsVirtBase : 1;
     unsigned NumberOfNonVirtBases : 31;
   };