diff --git a/caravel/viz.py b/caravel/viz.py
index 4c82afe850af6..4a0e6d358262a 100755
--- a/caravel/viz.py
+++ b/caravel/viz.py
@@ -1304,9 +1304,8 @@ def get_data(self):
         metric = self.form_data.get('metric')
         secondary_metric = self.form_data.get('secondary_metric')
         if metric == secondary_metric:
-            ndf = df[cols]
-            ndf['m1'] = df[metric]
-            ndf['m2'] = df[metric]
+            ndf = df
+            ndf.columns = [cols + ['m1', 'm2']]
         else:
             cols += [
                 self.form_data['metric'], self.form_data['secondary_metric']]