diff --git a/Orange/widgets/unsupervised/owlouvainclustering.py b/Orange/widgets/unsupervised/owlouvainclustering.py
index 1735238108e..be4e02484cf 100644
--- a/Orange/widgets/unsupervised/owlouvainclustering.py
+++ b/Orange/widgets/unsupervised/owlouvainclustering.py
@@ -136,6 +136,9 @@ def __init__(self):
 
     def _invalidate_pca_projection(self):
         self.pca_projection = None
+        if not self.apply_pca:
+            return
+
         self._invalidate_graph()
         self._set_modified(True)
 
diff --git a/Orange/widgets/unsupervised/tests/test_owlouvain.py b/Orange/widgets/unsupervised/tests/test_owlouvain.py
index 3bbbf86cf40..b2fb929788c 100644
--- a/Orange/widgets/unsupervised/tests/test_owlouvain.py
+++ b/Orange/widgets/unsupervised/tests/test_owlouvain.py
@@ -100,6 +100,38 @@ def test_do_not_recluster_on_same_data(self):
             self.commit_and_wait()
             self.assertEqual(call_count + 1, commit.call_count)
 
+    def test_only_recluster_when_necessary_pca_components_change(self):
+        # Compute clustering on some data
+        self.send_signal(self.widget.Inputs.data, self.iris)
+
+        # When PCA checkbox is ticked, any update to slider should invalidate results
+        self.widget.apply_pca_cbx.setChecked(True)
+        self.widget.pca_components_slider.setValue(2)
+        self.commit_and_wait()
+
+        with patch.object(self.widget, '_invalidate_output') as invalidate:
+            # Change slider value, this should invalidate output
+            self.widget.pca_components_slider.setValue(4)
+            self.commit_and_wait()
+            self.assertEqual(invalidate.call_count, 1)
+
+        with patch.object(self.widget, '_invalidate_output') as invalidate:
+            # Don't change slider value, this shouldn't do anything
+            self.widget.pca_components_slider.setValue(4)
+            self.commit_and_wait()
+            invalidate.assert_not_called()
+
+        # When PCA checkbox is not ticked updating the slider should have no effect
+        self.widget.apply_pca_cbx.setChecked(False)
+        self.widget.pca_components_slider.setValue(2)
+        self.commit_and_wait()
+
+        with patch.object(self.widget, '_invalidate_output') as invalidate:
+            # Change slider value, this should invalidate output
+            self.widget.pca_components_slider.setValue(4)
+            self.commit_and_wait()
+            invalidate.assert_not_called()
+
     def test_invalidate(self):
         # pylint: disable=protected-access
         data = self.iris