diff --git a/swh/model/model.py b/swh/model/model.py
--- a/swh/model/model.py
+++ b/swh/model/model.py
@@ -1564,6 +1564,12 @@
 
     @classmethod
     def from_dict(cls, d):
+        if "type" in d:
+            # Convert from old schema
+            type_ = d.pop("type")
+            if type_ == "origin":
+                d["target"] = str(Origin(d["target"]).swhid())
+
         d = {
             **d,
             "target": ExtendedSWHID.from_string(d["target"]),
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
@@ -1428,6 +1428,41 @@
     )
 
 
+def test_metadata_from_old_dict():
+    common_fields = {
+        "authority": {"type": "forge", "url": "https://forge.softwareheritage.org"},
+        "fetcher": {
+            "name": "test-fetcher",
+            "version": "0.0.1",
+        },
+        "discovery_date": _common_metadata_fields["discovery_date"],
+        "format": "json",
+        "metadata": b'{"origin": "https://example.com", "lines": "42"}',
+    }
+
+    m = RawExtrinsicMetadata(
+        target=_origin_swhid,
+        **common_fields,
+    )
+    assert (
+        RawExtrinsicMetadata.from_dict(
+            {"target": _origin_url, "type": "origin", **common_fields}
+        )
+        == m
+    )
+
+    m = RawExtrinsicMetadata(
+        target=_origin_swhid,
+        **common_fields,
+    )
+    assert (
+        RawExtrinsicMetadata.from_dict(
+            {"target": _content_swhid, "type": "content", **common_fields}
+        )
+        == m
+    )
+
+
 def test_metadata_to_dict():
     """Checks valid RawExtrinsicMetadata objects don't raise an error."""