diff --git a/Orange/widgets/visualize/owscatterplot.py b/Orange/widgets/visualize/owscatterplot.py
index 510ce0deb04..54c67ae845c 100644
--- a/Orange/widgets/visualize/owscatterplot.py
+++ b/Orange/widgets/visualize/owscatterplot.py
@@ -323,8 +323,9 @@ def set_data(self, data):
         self.vizrank.initialize()
         self.vizrank.attrs = self.data.domain.attributes if self.data is not None else []
         self.vizrank_button.setEnabled(
-            self.data is not None and self.data.domain.class_var is not None
-            and len(self.data.domain.attributes) > 1 and len(self.data) > 1)
+            self.data is not None and not self.data.is_sparse() and
+            self.data.domain.class_var is not None and
+            len(self.data.domain.attributes) > 1 and len(self.data) > 1)
         if self.data is not None and self.data.domain.class_var is None \
             and len(self.data.domain.attributes) > 1 and len(self.data) > 1:
             self.vizrank_button.setToolTip(
@@ -423,7 +424,6 @@ def prepare_data(self):
                             new=False)
 
     def sparse_to_dense(self, input_data=None):
-        self.vizrank_button.setEnabled(not (self.data and self.data.is_sparse()))
         if input_data is None or not input_data.is_sparse():
             return input_data
         keys = []
diff --git a/Orange/widgets/visualize/owscatterplotgraph.py b/Orange/widgets/visualize/owscatterplotgraph.py
index f5e01f2304c..45a4b89c0f8 100644
--- a/Orange/widgets/visualize/owscatterplotgraph.py
+++ b/Orange/widgets/visualize/owscatterplotgraph.py
@@ -989,7 +989,7 @@ def update_shapes(self):
         self.make_legend()
 
     def assure_attribute_present(self, attr):
-        if attr not in self.data.domain:
+        if self.data is not None and attr not in self.data.domain:
             self.master.prepare_data()
 
     def update_grid(self):