diff --git a/superset/legacy.py b/superset/legacy.py
index 8bec0846b2181..0782690fe8a95 100644
--- a/superset/legacy.py
+++ b/superset/legacy.py
@@ -63,8 +63,11 @@ def cast_form_data(form_data):
         elif v and ft == 'TextField' and field_config.get('isFloat'):
             v = float(v) if v != '' else None
         elif v and ft == 'SelectField':
-            if field_config.get('multi') and not isinstance(v, list):
-                v = [v]
+            if field_config.get('multi'):
+                if type(form_data).__name__ == 'ImmutableMultiDict':
+                    v = form_data.getlist(k)
+                elif not isinstance(v, list):
+                    v = [v]
         if d.get('slice_id'):
             d['slice_id'] = int(d['slice_id'])
 
diff --git a/superset/views.py b/superset/views.py
index f419abd9730cb..8882ba041f71d 100755
--- a/superset/views.py
+++ b/superset/views.py
@@ -1478,7 +1478,7 @@ def get_form_data(self):
 
         if request.args.get("viz_type"):
             # Converting old URLs
-            d = cast_form_data(request.args.to_dict())
+            d = cast_form_data(request.args)
 
         extra_filters = request.args.get("extra_filters")
         filters = d.get('filters', [])