diff --git a/larray_editor/arrayadapter.py b/larray_editor/arrayadapter.py
index 32d8f38..a8f44f4 100644
--- a/larray_editor/arrayadapter.py
+++ b/larray_editor/arrayadapter.py
@@ -14,9 +14,8 @@ def __init__(self, axes_model, xlabels_model, ylabels_model, data_model):
         self.ylabels_model = ylabels_model
         self.data_model = data_model
 
-        # these are not valid values, but should overwritten by set_data which must be called before the adapter is used
-        self.current_filter = None
-        self.changes = None
+        self.current_filter = {}
+        self.changes = {}
         self.la_data = None
         self.bg_value = None
         self.filtered_data = None
diff --git a/larray_editor/arraymodel.py b/larray_editor/arraymodel.py
index f6dbb1a..0654fc7 100644
--- a/larray_editor/arraymodel.py
+++ b/larray_editor/arraymodel.py
@@ -210,7 +210,7 @@ def __init__(self, parent=None, readonly=False, format="%.3f", font=None, minval
         self.minvalue = minvalue
         self.maxvalue = maxvalue
 
-        self.changes = None
+        self.changes = {}
         self.color_func = None
 
         self.vmin = None