diff --git a/orangecontrib/text/widgets/owstatistics.py b/orangecontrib/text/widgets/owstatistics.py
index 98a86c570..5fd928fa0 100644
--- a/orangecontrib/text/widgets/owstatistics.py
+++ b/orangecontrib/text/widgets/owstatistics.py
@@ -408,7 +408,8 @@ def __call__(self, data: Corpus) -> np.ndarray:
         return self.function(data, self.pattern, self.source, lambda: True)[0]
 
     def __eq__(self, other):
-        return self.function == other.function and self.pattern == other.pattern
+        return type(self) is type(other) and self.function == other.function \
+            and self.pattern == other.pattern
 
     def __hash__(self):
         return hash((self.function, self.pattern))
diff --git a/orangecontrib/text/widgets/tests/test_owstatistics.py b/orangecontrib/text/widgets/tests/test_owstatistics.py
index 20e3a8ca1..fc9a9abdf 100644
--- a/orangecontrib/text/widgets/tests/test_owstatistics.py
+++ b/orangecontrib/text/widgets/tests/test_owstatistics.py
@@ -4,6 +4,7 @@
 from AnyQt.QtWidgets import QPushButton
 
 from Orange.data import Domain, StringVariable
+from Orange.preprocess import SklImpute
 from Orange.widgets.tests.base import WidgetTest
 from Orange.widgets.tests.utils import simulate
 from orangecontrib.text import Corpus
@@ -521,6 +522,12 @@ def test_migrate_settings(self):
         ]
         self.assertListEqual(expected, widget.active_rules)
 
+    def test_preprocess_output(self):
+        self.send_signal(self.widget.Inputs.corpus, self.corpus)
+        output = self.get_output(self.widget.Outputs.corpus)
+        imputed = SklImpute()(output)
+        self.assertIsNotNone(imputed)
+
 
 if __name__ == "__main__":
     unittest.main()