diff --git a/swh/loader/package/nixguix/loader.py b/swh/loader/package/nixguix/loader.py
--- a/swh/loader/package/nixguix/loader.py
+++ b/swh/loader/package/nixguix/loader.py
@@ -4,6 +4,7 @@
 # See top-level LICENSE file for more information
 
 import json
+import logging
 import requests
 
 from typing import Dict, Optional, Any, Mapping
@@ -19,6 +20,9 @@
 from swh.loader.package.loader import PackageLoader
 
 
+logger = logging.getLogger(__name__)
+
+
 def retrieve_sources(url: str) -> Dict[str, Any]:
     response = requests.get(url,
                             allow_redirects=True)
@@ -29,6 +33,59 @@
     return json.loads(response.content.decode('utf-8'))
 
 
+def clean_sources(sources: Dict[str, Any]) -> Dict[str, Any]:
+    """Validate and clean the sources structure. First, it ensures all top
+    level keys are presents. Then, it walks on the sources list
+    and removes sources that don't contain required keys.
+
+    Raises:
+      ValueError: if a top level key is missing
+
+    """
+    # Required top level keys
+    required_keys = ['version', 'revision', 'sources']
+    missing_keys = []
+    for required_key in required_keys:
+        if required_key not in sources:
+            missing_keys.append(required_key)
+
+    if missing_keys != []:
+        raise ValueError("sources structure invalid, missing: %s",
+                         ",".join(missing_keys))
+
+    # Only the version 1 is currently supported
+    if sources['version'] != 1:
+        raise ValueError("The sources structure version '%d' is not supported",
+                         sources['version'])
+
+    # If a source doesn't contain required attributes, this source is
+    # skipped but others could still be archived.
+    verified_sources = []
+    for source in sources['sources']:
+        valid = True
+        required_keys = ['urls', 'integrity', 'type']
+        for required_key in required_keys:
+            if required_key not in source:
+                logger.info("Skip source '%s' because key '%s' is missing",
+                            source, required_key)
+                valid = False
+        if source['type'] != 'url':
+            logger.info(
+                "Skip source '%s' because the type %s is not supported",
+                source, source['type'])
+            valid = False
+        if not isinstance(source['urls'], list):
+            logger.info(
+                "Skip source '%s' because the urls attribute is not a list",
+                source)
+            valid = False
+        if valid:
+            verified_sources.append(source)
+
+    sources['sources'] = verified_sources
+    return sources
+
+
 class NixGuixLoader(PackageLoader):
     """Load sources from a sources.json file. This loader is used to load
     sources used by functional package manager (eg. Nix and Guix).
@@ -38,8 +95,9 @@
 
     def __init__(self, url):
         super().__init__(url=url)
-        s = retrieve_sources(url)
-        self.sources = s['sources']
+        raw = retrieve_sources(url)
+        clean = clean_sources(raw)
+        self.sources = clean['sources']
         self.provider_url = url
 
         self._integrityByUrl = {s['urls'][0]: s['integrity']
@@ -48,7 +106,7 @@
         # The revision used to create the sources.json file. For Nix,
         # this revision belongs to the github.com/nixos/nixpkgs
         # repository
-        self.revision = s['revision']
+        self.revision = clean['revision']
 
     # Note: this could be renamed get_artifacts in the PackageLoader
     # base class.
diff --git a/swh/loader/package/nixguix/tests/test_nixguix.py b/swh/loader/package/nixguix/tests/test_nixguix.py
--- a/swh/loader/package/nixguix/tests/test_nixguix.py
+++ b/swh/loader/package/nixguix/tests/test_nixguix.py
@@ -7,7 +7,7 @@
 from json.decoder import JSONDecodeError
 
 from swh.loader.package.nixguix.loader import (
-    NixGuixLoader, retrieve_sources
+    NixGuixLoader, retrieve_sources, clean_sources
 )
 
 from swh.loader.package.tests.common import (
@@ -33,6 +33,60 @@
         NixGuixLoader('https://example.com/file.txt')
 
 
+def test_clean_sources_invalid_schema(swh_config, requests_mock_datadir):
+    sources = {}
+    with pytest.raises(ValueError,
+                       match="sources structure invalid, missing: .*"):
+        clean_sources(sources)
+
+
+def test_clean_sources_invalid_version(swh_config, requests_mock_datadir):
+    sources = {
+        'version': 2,
+        'sources': [],
+        'revision': 'my-revision'
+    }
+
+    with pytest.raises(ValueError,
+                       match="sources structure version .* is not supported"):
+        clean_sources(sources)
+
+
+def test_clean_sources_invalid_sources(swh_config, requests_mock_datadir):
+    sources = {
+        'version': 1,
+        'sources': [
+            # Valid source
+            {
+                'type': 'url',
+                'urls': ['my-url'],
+                'integrity': 'my-integrity'
+            },
+            # integrity is missing
+            {
+                'type': 'url',
+                'urls': ['my-url'],
+            },
+            # urls is not a list
+            {
+                'type': 'url',
+                'urls': 'my-url',
+                'integrity': 'my-integrity'
+            },
+            # type is not url
+            {
+                'type': 'git',
+                'urls': ['my-url'],
+                'integrity': 'my-integrity'
+            }
+        ],
+        'revision': 'my-revision'
+    }
+    clean = clean_sources(sources)
+
+    assert len(clean['sources']) == 1
+
+
 def test_loader_one_visit(swh_config, requests_mock_datadir):
     loader = NixGuixLoader(sources_url)
     res = loader.load()
diff --git a/swh/loader/package/nixguix/tests/test_tasks.py b/swh/loader/package/nixguix/tests/test_tasks.py
--- a/swh/loader/package/nixguix/tests/test_tasks.py
+++ b/swh/loader/package/nixguix/tests/test_tasks.py
@@ -12,6 +12,7 @@
     mock_retrieve_sources = mocker.patch(
         'swh.loader.package.nixguix.loader.retrieve_sources')
     mock_retrieve_sources.return_value = {
+        'version': 1,
         'sources': [],
         'revision': 'some-revision'
     }