diff --git a/src/omero/gateway/__init__.py b/src/omero/gateway/__init__.py
index 229af9d59..a225ea66c 100644
--- a/src/omero/gateway/__init__.py
+++ b/src/omero/gateway/__init__.py
@@ -6656,7 +6656,10 @@ def getGridSize(self):
                     "where plate.id = :id"
             res = q.projection(query, params, self._conn.SERVICE_OPTS)
             (row, col) = res[0]
-            self._gridSize = {'rows': row.val+1, 'columns': col.val+1}
+            if row is None or col is None:
+                self._gridSize = {'rows': 0, 'columns': 0}
+            else:
+                self._gridSize = {'rows': row.val+1, 'columns': col.val+1}
         return self._gridSize
 
     def getWellGrid(self, index=0):