diff --git a/superset/viz.py b/superset/viz.py
index e59835b60baf..18a3d3ab70a5 100644
--- a/superset/viz.py
+++ b/superset/viz.py
@@ -1956,7 +1956,8 @@ def get_properties(self, d):
 
     def get_data(self, df):
         fd = self.form_data
-        self.point_radius_fixed = fd.get('point_radius_fixed')
+        self.point_radius_fixed = (
+            fd.get('point_radius_fixed') or {'type': 'fix', 'value': 500})
         self.fixed_value = None
         self.dim = self.form_data.get('dimension')
         if self.point_radius_fixed.get('type') != 'metric':