diff --git a/Orange/widgets/tests/base.py b/Orange/widgets/tests/base.py
index 8e07cb0f9d6..89b156e41f7 100644
--- a/Orange/widgets/tests/base.py
+++ b/Orange/widgets/tests/base.py
@@ -967,15 +967,17 @@ def test_plot_once(self, timeout=DEFAULT_TIMEOUT):
         self.widget.setup_plot = Mock()
         self.widget.commit = Mock()
         self.send_signal(self.widget.Inputs.data, table)
-        self.widget.setup_plot.assert_called_once()
-        self.widget.commit.assert_called_once()
-
         if self.widget.isBlocking():
             spy = QSignalSpy(self.widget.blockingStateChanged)
             self.assertTrue(spy.wait(timeout))
+        self.widget.setup_plot.assert_called_once()
+        self.widget.commit.assert_called_once()
 
         self.widget.commit.reset_mock()
         self.send_signal(self.widget.Inputs.data_subset, table[::10])
+        if self.widget.isBlocking():
+            spy = QSignalSpy(self.widget.blockingStateChanged)
+            self.assertTrue(spy.wait(timeout))
         self.widget.setup_plot.assert_called_once()
         self.widget.commit.assert_called_once()
 
diff --git a/Orange/widgets/unsupervised/tests/test_owmds.py b/Orange/widgets/unsupervised/tests/test_owmds.py
index 01a1a914172..2a3c95bfd7e 100644
--- a/Orange/widgets/unsupervised/tests/test_owmds.py
+++ b/Orange/widgets/unsupervised/tests/test_owmds.py
@@ -49,6 +49,23 @@ def tearDown(self):
         self.widget.onDeleteWidget()
         super().tearDown()
 
+    def test_plot_once(self, timeout=5000):
+        """Test if data is plotted only once but committed on every input change"""
+        table = Table("heart_disease")
+        self.widget.setup_plot = Mock()
+        self.widget.commit = Mock()
+        self.send_signal(self.widget.Inputs.data, table)
+        self.widget.commit.reset_mock()
+        self.wait_until_stop_blocking()
+        self.widget.setup_plot.assert_called_once()
+        self.widget.commit.assert_called_once()
+
+        self.widget.commit.reset_mock()
+        self.send_signal(self.widget.Inputs.data_subset, table[::10])
+        self.wait_until_stop_blocking()
+        self.widget.setup_plot.assert_called_once()
+        self.widget.commit.assert_called_once()
+
     def test_pca_init(self):
         self.send_signal(self.signal_name, self.signal_data)
         output = self.get_output(self.widget.Outputs.annotated_data, wait=1000)