diff --git a/superset/views/core.py b/superset/views/core.py
index 3db014bbd634..87a121d21654 100755
--- a/superset/views/core.py
+++ b/superset/views/core.py
@@ -1276,7 +1276,9 @@ def explore(self, datasource_type=None, datasource_id=None):
             title = _("Explore - %(table)s", table=table_name)
         return self.render_template(
             "superset/basic.html",
-            bootstrap_data=json.dumps(bootstrap_data),
+            bootstrap_data=json.dumps(
+                bootstrap_data, default=utils.pessimistic_json_iso_dttm_ser
+            ),
             entry="explore",
             title=title,
             standalone_mode=standalone,
@@ -2186,14 +2188,18 @@ def dashboard(**kwargs):
         }
 
         if request.args.get("json") == "true":
-            return json_success(json.dumps(bootstrap_data))
+            return json_success(
+                json.dumps(bootstrap_data, default=utils.pessimistic_json_iso_dttm_ser)
+            )
 
         return self.render_template(
             "superset/dashboard.html",
             entry="dashboard",
             standalone_mode=standalone_mode,
             title=dash.dashboard_title,
-            bootstrap_data=json.dumps(bootstrap_data),
+            bootstrap_data=json.dumps(
+                bootstrap_data, default=utils.pessimistic_json_iso_dttm_ser
+            ),
         )
 
     @api
@@ -2990,7 +2996,9 @@ def profile(self, username):
             "superset/basic.html",
             title=_("%(user)s's profile", user=username),
             entry="profile",
-            bootstrap_data=json.dumps(payload, default=utils.json_iso_dttm_ser),
+            bootstrap_data=json.dumps(
+                payload, default=utils.pessimistic_json_iso_dttm_ser
+            ),
         )
 
     @has_access
diff --git a/tests/core_tests.py b/tests/core_tests.py
index 1e640493d3a7..50605a903696 100644
--- a/tests/core_tests.py
+++ b/tests/core_tests.py
@@ -963,11 +963,16 @@ def test_feature_flag_serialization(self):
         )
         html = cgi.escape(encoded).replace("'", "'").replace('"', """)
 
-        data = self.get_resp("/superset/sqllab")
-        self.assertTrue(html in data)
-
-        data = self.get_resp("/superset/welcome")
-        self.assertTrue(html in data)
+        urls = [
+            "/superset/sqllab",
+            "/superset/welcome",
+            "/superset/dashboard/1/",
+            "/superset/profile/admin/",
+            "/superset/explore/table/1",
+        ]
+        for url in urls:
+            data = self.get_resp(url)
+            self.assertTrue(html in data)
 
 
 if __name__ == "__main__":