diff --git a/superset/views/core.py b/superset/views/core.py
index 7d65026a3bab..c1cee6d2c4ba 100755
--- a/superset/views/core.py
+++ b/superset/views/core.py
@@ -1629,7 +1629,12 @@ def dashboard(self, dashboard_id):
             qry = qry.filter_by(slug=dashboard_id)
 
         dash = qry.one()
-        datasources = {slc.datasource for slc in dash.slices}
+        datasources = set()
+        for slc in dash.slices:
+            datasource = slc.datasource
+            if datasource:
+                datasources.add(datasource)
+
         for datasource in datasources:
             if datasource and not self.datasource_access(datasource):
                 flash(