diff --git a/src/eval/stmt.rs b/src/eval/stmt.rs
index 5994236e..9dbf5433 100644
--- a/src/eval/stmt.rs
+++ b/src/eval/stmt.rs
@@ -141,7 +141,10 @@ impl Engine {
             let args = &mut [lhs_ptr_inner, &mut new_val];
 
             match self.call_native_fn(global, state, lib, op, hash, args, true, true, op_pos) {
-                Ok(_) => self.check_data_size(&mut args[0], root.1)?,
+                Ok(_) => {
+                    #[cfg(not(feature = "unchecked"))]
+                    self.check_data_size(&mut args[0], root.1)?;
+                }
                 Err(err) if matches!(*err, ERR::ErrorFunctionNotFound(ref f, _) if f.starts_with(op)) =>
                 {
                     // Expand to `var = var op rhs`