diff --git a/Orange/widgets/visualize/owmosaic.py b/Orange/widgets/visualize/owmosaic.py
index 045ac9b9a0c..e8cc5c889e5 100644
--- a/Orange/widgets/visualize/owmosaic.py
+++ b/Orange/widgets/visualize/owmosaic.py
@@ -3,6 +3,7 @@
 from itertools import product, chain, repeat
 from math import sqrt, log
 from operator import mul, attrgetter
+from typing import Set
 
 import numpy as np
 from scipy.stats import distributions
@@ -12,7 +13,7 @@
 from AnyQt.QtWidgets import (
     QGraphicsScene, QGraphicsLineItem, QGraphicsItemGroup)
 
-from Orange.data import Table, filter, Variable, Domain
+from Orange.data import Table, filter, Variable, Domain, DiscreteVariable
 from Orange.data.sql.table import SqlTable, LARGE_TABLE, DEFAULT_SAMPLE_TIME
 from Orange.preprocess import Discretize
 from Orange.preprocess.discretize import EqualFreq
@@ -286,12 +287,12 @@ class Outputs:
     vizrank = SettingProvider(MosaicVizRank)
     settings_version = 2
     use_boxes = Setting(True)
-    variable1 = ContextSetting(None)
-    variable2 = ContextSetting(None)
-    variable3 = ContextSetting(None)
-    variable4 = ContextSetting(None)
-    variable_color = ContextSetting(None)
-    selection = Setting(set(), schema_only=True)
+    variable1: Variable = ContextSetting(None)
+    variable2: Variable = ContextSetting(None)
+    variable3: Variable = ContextSetting(None)
+    variable4: Variable = ContextSetting(None)
+    variable_color: DiscreteVariable = ContextSetting(None)
+    selection: Set[str] = Setting(set(), schema_only=True)
 
     BAR_WIDTH = 5
     SPACING = 4