diff --git a/site-modules/profile/files/prometheus/update-prometheus-config b/site-modules/profile/files/prometheus/update-prometheus-config
index a0ec8e13..c111608e 100755
--- a/site-modules/profile/files/prometheus/update-prometheus-config
+++ b/site-modules/profile/files/prometheus/update-prometheus-config
@@ -1,115 +1,116 @@
 #!/usr/bin/env python3
 #
 # This generates a static configuration for Prometheus
 #
 # Copyright © 2020 The Software Heritage Developers.
 # This file is released under the Apache-2.0 License.
 #
 
 from collections import defaultdict
 import copy
 from dataclasses import asdict, dataclass, fields
 import datetime
 import os
 import stat
 import sys
 from typing import Any, Dict, Iterable, List, Optional
 
 import yaml
 
 
 @dataclass(frozen=True)
 class JobGroup:
     """Job parameters from which to group prometheus jobs"""
 
     job_name: str
     scrape_interval: Optional[int]
     scrape_timeout: Optional[int]
     metrics_path: Optional[str]
     scheme: Optional[str]
 
     @classmethod
     def from_dict(cls, dict):
         init_vars = {field.name: dict.get(field.name) for field in fields(cls)}
+
         if init_vars.get('metrics_path') == '/metrics':
-            del init_vars['metrics_path']
+            init_vars['metrics_path'] = None
 
         if init_vars.get('scheme') == 'http':
-            del init_vars['scheme']
+            init_vars['scheme'] = None
 
         return cls(**init_vars)
 
 
 def load_yaml_from_dir(dirname: str) -> Iterable[Dict[str, Any]]:
     """Load all yaml files from a given directory"""
     for filename in os.listdir(dirname):
         if not filename.endswith((".yml", ".yaml")):
             continue
 
         path = os.path.join(dirname, filename)
         with open(path, "r") as f:
             yield from yaml.safe_load(f)
 
 
 def generate_scrape_configs(configs: Dict[JobGroup, List[Dict[str, Any]]]):
     """Generate a scrape_configs entry from a dict"""
     for params, targets in configs.items():
         yield {
             **{
                 param: value
                 for param, value in asdict(params).items()
                 if value is not None
             },
             "static_configs": targets,
         }
 
 
 def merge_prometheus_config(
     base_config: Dict[str, Any], scrape_configs: Iterable[Dict[str, Any]]
 ) -> Dict[str, Any]:
     """Merge the main prometheus config with scrape configs"""
     config = copy.deepcopy(base_config)
     config.setdefault("scrape_configs", []).extend(scrape_configs)
     return config
 
 
 def replace_file(old_file, new_file):
     """Replace old_file with new_file, ensuring permissions are the same"""
 
     try:
         info = os.stat(old_file)
         os.chown(new_file, info.st_uid, info.st_gid)
         os.chmod(new_file, stat.S_IMODE(info.st_mode))
     except FileNotFoundError:
         pass
 
     os.rename(new_file, old_file)
 
 
 if __name__ == "__main__":
     base_conffile = sys.argv[1]
     exported_dir = sys.argv[2]
     output = sys.argv[3]
     config_groups: Dict[JobGroup, List[Dict[str, Any]]] = defaultdict(list)
 
     for conf in load_yaml_from_dir(exported_dir):
         group = JobGroup.from_dict(conf)
         for key in asdict(group):
             conf.pop(key, None)
         config_groups[group].append(conf)
 
     with open(base_conffile, "r") as f:
         base_config = yaml.safe_load(f)
 
     full_config = merge_prometheus_config(
         base_config, generate_scrape_configs(config_groups),
     )
 
     now = datetime.datetime.now(tz=datetime.timezone.utc).isoformat()
     with open(output + ".tmp", "w") as f:
         print(f"# This file was generated by {sys.argv[0]} on {now}.", file=f)
         print(f"# Changes will be lost", file=f)
         print(f"", file=f)
         yaml.dump(full_config, f, default_flow_style=False)
 
     replace_file(output, output + ".tmp")