diff --git a/src/vim9execute.c b/src/vim9execute.c
index 882b13c..3bcdce4 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -4455,7 +4455,11 @@
 		else
 		{
 		    *tv = *STACK_TV_VAR(0);
-		    ++tv->vval.v_object->obj_refcount;
+		    object_T *obj = tv->vval.v_object;
+		    ++obj->obj_refcount;
+
+		    // Lock all the constant object variables
+		    obj_lock_const_vars(obj);
 		}
 		// FALLTHROUGH