diff --git a/awkward-cpp/include/awkward/io/json.h b/awkward-cpp/include/awkward/io/json.h
index 6eaf19735f..eb45499cde 100644
--- a/awkward-cpp/include/awkward/io/json.h
+++ b/awkward-cpp/include/awkward/io/json.h
@@ -61,6 +61,9 @@ namespace awkward {
              int64_t initial,
              double resize);
 
+    // Delete copy constructor
+    FromJsonObjectSchema(const FromJsonObjectSchema&) = delete;
+
     /// @brief HERE
     inline int64_t current_stack_depth() const noexcept {
       return current_stack_depth_;