diff --git a/swh/model/identifiers.py b/swh/model/identifiers.py
index a1719b6bb6cb1b2f7d0766c828cc58afe6dd507a..3d06f9d5c2c32a80d211b55cb0a52d08b651b778 100644
--- a/swh/model/identifiers.py
+++ b/swh/model/identifiers.py
@@ -265,8 +265,8 @@ def revision_identifier(revision):
     ])
 
     metadata = revision.get('metadata', {})
-    if 'extra-headers' in metadata:
-        headers = metadata['extra-headers']
+    if 'extra_headers' in metadata:
+        headers = metadata['extra_headers']
         keys = list(headers.keys())
         keys.sort()
         for header_key in keys:
diff --git a/swh/model/tests/test_identifiers.py b/swh/model/tests/test_identifiers.py
index b37b15115042bb3f4f4e6a6f7a1b865b30914f6d..7864ec69fb1f11fa246b9fd5bc4d84726c761151 100644
--- a/swh/model/tests/test_identifiers.py
+++ b/swh/model/tests/test_identifiers.py
@@ -289,7 +289,7 @@ class RevisionIdentifier(unittest.TestCase):
                                                 tzinfo=linus_tz),
             'message': b'Linux 4.2-rc2\n',
             'metadata': {
-                'extra-headers': {
+                'extra_headers': {
                     'svn-revision': 10,
                     'svn-repo-uuid': '046f1af7-66c2-d61b-5410-ce57b7db7bff',
                 }