diff --git a/swh/deposit/api/checks.py b/swh/deposit/api/checks.py
--- a/swh/deposit/api/checks.py
+++ b/swh/deposit/api/checks.py
@@ -35,10 +35,9 @@
 
     for field, value in metadata.items():
         for possible_names in alternate_fields:
-            for possible_name in possible_names:
-                if possible_name in field:
-                    alternate_fields[possible_names] = True
-                    continue
+            if field in possible_names:
+                alternate_fields[possible_names] = True
+                continue
 
     mandatory_result = [" or ".join(k) for k, v in alternate_fields.items() if not v]
 
diff --git a/swh/deposit/tests/api/test_checks.py b/swh/deposit/tests/api/test_checks.py
--- a/swh/deposit/tests/api/test_checks.py
+++ b/swh/deposit/tests/api/test_checks.py
@@ -81,6 +81,18 @@
                 "fields": ["atom:author or codemeta:author"],
             },
         ),
+        (
+            {
+                "atom:url": "something",
+                "atom:external_identifier": "something-else",
+                "atom:title": "foobar",
+                "atom:authorblahblah": "foo",
+            },
+            {
+                "summary": "Mandatory fields are missing",
+                "fields": ["atom:author or codemeta:author"],
+            },
+        ),
     ],
 )
 def test_api_checks_check_metadata_ko(