diff --git a/swh/model/identifiers.py b/swh/model/identifiers.py
--- a/swh/model/identifiers.py
+++ b/swh/model/identifiers.py
@@ -417,7 +417,7 @@
     - author_date
     - committer
     - committer_date
-    - metadata -> extra_headers
+    - extra_headers or metadata -> extra_headers
     - message
 
     A revision's identifier is the 'git'-checksum of a commit manifest
@@ -477,12 +477,12 @@
     )
 
     # Handle extra headers
-    metadata = revision.get("metadata")
-    if not metadata:
-        metadata = {}
-
-    for key, value in metadata.get("extra_headers", []):
+    metadata = revision.get("metadata") or {}
+    extra_headers = revision.get("extra_headers", ())
+    if not extra_headers and "extra_headers" in metadata:
+        extra_headers = metadata["extra_headers"]
 
+    for key, value in extra_headers:
         # Integer values: decimal representation
         if isinstance(value, int):
             value = str(value).encode("utf-8")
diff --git a/swh/model/model.py b/swh/model/model.py
--- a/swh/model/model.py
+++ b/swh/model/model.py
@@ -6,6 +6,7 @@
 import datetime
 
 from abc import ABCMeta, abstractmethod
+from copy import deepcopy
 from enum import Enum
 from hashlib import sha256
 from typing import Dict, Optional, Tuple, TypeVar, Union
@@ -435,6 +436,21 @@
     )
     parents = attr.ib(type=Tuple[Sha1Git, ...], validator=type_validator(), default=())
     id = attr.ib(type=Sha1Git, validator=type_validator(), default=b"")
+    extra_headers = attr.ib(
+        type=Tuple[Tuple[str, Union[int, str, bytes]], ...],
+        validator=type_validator(),
+        default=(),
+    )
+
+    def __attrs_post_init__(self):
+        super().__attrs_post_init__()
+        # ensure metadata is a deep copy of whatever was given, and if needed
+        # extract extra_headers from there
+        if self.metadata:
+            metadata = deepcopy(self.metadata)
+            if not self.extra_headers and "extra_headers" in metadata:
+                object.__setattr__(self, "extra_headers", metadata.pop("extra_headers"))
+            object.__setattr__(self, "metadata", metadata)
 
     @staticmethod
     def compute_hash(object_dict):
diff --git a/swh/model/tests/test_model.py b/swh/model/tests/test_model.py
--- a/swh/model/tests/test_model.py
+++ b/swh/model/tests/test_model.py
@@ -415,6 +415,35 @@
         SkippedContent.from_dict(skipped_content_d)
 
 
+# Revision
+
+
+def test_revision_extra_headers():
+    rev_dict = revision_example.copy()
+    rev_dict.pop("id")
+    rev_model = Revision.from_dict(rev_dict)
+    assert rev_model.metadata is None
+    assert rev_model.extra_headers == ()
+
+    rev_dict["metadata"] = {
+        "something": "somewhere",
+        "some other thing": "stranger",
+    }
+    rev_model = Revision.from_dict(rev_dict)
+    assert rev_model.metadata == rev_dict["metadata"]
+    assert rev_model.extra_headers == ()
+
+    rev_dict["metadata"]["extra_headers"] = (
+        ("header1", "value1"),
+        ("header2", 42),
+        ("header3", b"should I?\u0000"),
+        ("header1", "again"),
+    )
+    rev_model = Revision.from_dict(rev_dict)
+    assert "extra_headers" not in rev_model.metadata
+    assert rev_model.extra_headers == rev_dict["metadata"]["extra_headers"]
+
+
 # ID computation