Index: main/grid/hash-data.lisp
===================================================================
--- main/grid/hash-data.lisp	(revision main,60)
+++ main/grid/hash-data.lisp	(revision main,68)
@@ -6,4 +6,12 @@
   ((row-tables :type (vector hash-table) :initarg :row-tables)
    (keys :type vector :initarg :keys)))
+
+(defmethod initialize-instance ((data hash-per-row-grid-data) &rest init-args
+                                &key row-tables keys &allow-other-keys)
+  (apply #'call-next-method
+         data
+         :row-tables (coerce row-tables 'vector)
+         :keys (coerce keys 'vector)
+         init-args))
 
 (defmethod rows ((d hash-per-row-grid-data))