diff --git a/include/xgboost/json.h b/include/xgboost/json.h
index 473b0f1d5..74bab68d9 100644
--- a/include/xgboost/json.h
+++ b/include/xgboost/json.h
@@ -58,7 +58,9 @@ class Value {
   virtual Json& operator[](int ind);
 
   virtual bool operator==(Value const& rhs) const = 0;
+#if !defined(__APPLE__)
   virtual Value& operator=(Value const& rhs) = delete;
+#endif  // !defined(__APPLE__)
 
   std::string TypeStr() const;