diff --git a/Orange/widgets/data/owpaintdata.py b/Orange/widgets/data/owpaintdata.py
index 42a69ff82d3..1dd030e1808 100644
--- a/Orange/widgets/data/owpaintdata.py
+++ b/Orange/widgets/data/owpaintdata.py
@@ -1226,18 +1226,16 @@ def pen(color):
             self.plot.removeItem(self._scatter_item)
             self._scatter_item = None
 
-        nclasses = len(self.class_model)
-        pens = [pen(self.colors[i]) for i in range(nclasses)]
-
         x = self.__buffer[:, 0].copy()
         if self.hasAttr2:
             y = self.__buffer[:, 1].copy()
         else:
             y = np.zeros(self.__buffer.shape[0])
-        pen = [pens[ci] for ci in self.__buffer[:, 2].astype(int)]
 
+        colors = self.colors[self.__buffer[:, 2]]
+        pens = [pen(c) for c in colors]
         self._scatter_item = pg.ScatterPlotItem(
-            x, y, symbol="+", pen=pen
+            x, y, symbol="+", pen=pens
         )
         self.plot.addItem(self._scatter_item)
 
diff --git a/Orange/widgets/data/tests/test_owpaintdata.py b/Orange/widgets/data/tests/test_owpaintdata.py
index 6ff2cefa2de..34810433720 100644
--- a/Orange/widgets/data/tests/test_owpaintdata.py
+++ b/Orange/widgets/data/tests/test_owpaintdata.py
@@ -7,7 +7,7 @@
 from Orange.data import Table
 from Orange.widgets.data import owpaintdata
 from Orange.widgets.data.owpaintdata import OWPaintData
-from Orange.widgets.tests.base import WidgetTest
+from Orange.widgets.tests.base import WidgetTest, datasets
 
 
 class TestOWPaintData(WidgetTest):
@@ -25,6 +25,10 @@ def test_empty_data(self):
         self.send_signal("Data", data)
         self.send_signal("Data", Table(data.domain))
 
+    def test_nan_data(self):
+        data = datasets.missing_data_2()
+        self.send_signal("Data", data)
+
     def test_output_shares_internal_buffer(self):
         data = Table("iris")[::5]
         self.send_signal("Data", data)