diff --git a/include/clang/AST/VTableBuilder.h b/include/clang/AST/VTableBuilder.h
index ac71441..bcbe875 100644
--- a/include/clang/AST/VTableBuilder.h
+++ b/include/clang/AST/VTableBuilder.h
@@ -256,6 +256,7 @@
 
     uint64_t AddressPoint = AddressPoints.lookup(Base);
     assert(AddressPoint != 0 || IsMicrosoftABI);
+    (void)IsMicrosoftABI;
 
     return AddressPoint;
   }