diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -1,5 +1,5 @@
 swh.core >= 0.0.7
 swh.loader.core >= 0.18.0
-swh.model >= 0.4.0
+swh.model >= 2.9.0
 swh.scheduler >= 0.0.39
 swh.storage >= 0.22.0
diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
 dulwich >= 0.18.7
 retrying
 click
+typing-extensions
diff --git a/swh/loader/git/converters.py b/swh/loader/git/converters.py
--- a/swh/loader/git/converters.py
+++ b/swh/loader/git/converters.py
@@ -15,6 +15,7 @@
     Content,
     Directory,
     DirectoryEntry,
+    HashableObject,
     ObjectType,
     Person,
     Release,
@@ -26,7 +27,18 @@
     TimestampWithTimezone,
 )
 
-HASH_ALGORITHMS = DEFAULT_ALGORITHMS - {"sha1_git"}
+
+class HashMismatch(Exception):
+    pass
+
+
+def check_id(obj: HashableObject) -> None:
+    real_id = obj.compute_hash()
+    if obj.id != real_id:
+        raise HashMismatch(
+            f"Expected {type(obj).__name__} hash to be {obj.id.hex()}, "
+            f"got {real_id.hex()}"
+        )
 
 
 def dulwich_blob_to_content_id(obj: ShaFile) -> Dict[str, Any]:
@@ -37,8 +49,12 @@
 
     size = blob.raw_length()
     data = blob.as_raw_string()
-    hashes = MultiHash.from_data(data, HASH_ALGORITHMS).digest()
-    hashes["sha1_git"] = blob.sha().digest()
+    hashes = MultiHash.from_data(data, DEFAULT_ALGORITHMS).digest()
+    if hashes["sha1_git"] != blob.sha().digest():
+        raise HashMismatch(
+            f"Expected Content hash to be {blob.sha().digest().hex()}, "
+            f"got {hashes['sha1_git'].hex()}"
+        )
     hashes["length"] = size
     return hashes
 
@@ -84,7 +100,9 @@
             )
         )
 
-    return Directory(id=tree.sha().digest(), entries=tuple(entries),)
+    dir_ = Directory(id=tree.sha().digest(), entries=tuple(entries),)
+    check_id(dir_)
+    return dir_
 
 
 def parse_author(name_email: bytes) -> Person:
@@ -124,7 +142,7 @@
     if commit.gpgsig:
         extra_headers.append((b"gpgsig", commit.gpgsig))
 
-    return Revision(
+    rev = Revision(
         id=commit.sha().digest(),
         author=parse_author(commit.author),
         date=dulwich_tsinfo_to_timestamp(
@@ -142,6 +160,8 @@
         synthetic=False,
         parents=tuple(bytes.fromhex(p.decode()) for p in commit.parents),
     )
+    check_id(rev)
+    return rev
 
 
 DULWICH_TARGET_TYPES = {
@@ -181,7 +201,7 @@
     if tag.signature:
         message += tag.signature
 
-    return Release(
+    rel = Release(
         id=tag.sha().digest(),
         author=author,
         date=date,
@@ -192,3 +212,5 @@
         metadata=None,
         synthetic=False,
     )
+    check_id(rel)
+    return rel
diff --git a/swh/loader/git/tests/test_converters.py b/swh/loader/git/tests/test_converters.py
--- a/swh/loader/git/tests/test_converters.py
+++ b/swh/loader/git/tests/test_converters.py
@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import copy
 import os
 import shutil
 import subprocess
@@ -12,7 +13,7 @@
 import pytest
 
 import swh.loader.git.converters as converters
-from swh.model.hashutil import bytehex_to_hash, hash_to_bytes
+from swh.model.hashutil import bytehex_to_hash, hash_to_bytehex, hash_to_bytes
 from swh.model.model import (
     Content,
     ObjectType,
@@ -89,6 +90,7 @@
 
     def __init__(
         self,
+        sha,
         name,
         type_name,
         target,
@@ -99,6 +101,7 @@
         message,
         signature,
     ):
+        self._sha = sha
         self.name = name
         self.type_name = type_name
         self.object = SWHObjectType(target_type), target
@@ -110,9 +113,11 @@
         self._tag_timezone_neg_utc = False
 
     def sha(self):
-        from hashlib import sha1
+        class hasher:
+            def digest():
+                return self._sha
 
-        return sha1()
+        return hasher
 
 
 @pytest.mark.fs
@@ -161,13 +166,34 @@
         )
         assert content == expected_content
 
+    def test_corrupt_blob(self, mocker):
+        # has a signature
+        sha1 = hash_to_bytes("28c6f4023d65f74e3b59a2dea3c4277ed9ee07b0")
+
+        blob = copy.deepcopy(self.repo[hash_to_bytehex(sha1)])
+
+        class hasher:
+            def digest():
+                return sha1
+
+        blob._sha = hasher
+
+        converters.dulwich_blob_to_content(blob)
+        converters.dulwich_blob_to_content_id(blob)
+
+        sha1 = hash_to_bytes("1234" * 10)
+
+        with pytest.raises(converters.HashMismatch):
+            converters.dulwich_blob_to_content(blob)
+        with pytest.raises(converters.HashMismatch):
+            converters.dulwich_blob_to_content_id(blob)
+
     def test_convertion_wrong_input(self):
         class Something:
             type_name = b"something-not-the-right-type"
 
         m = {
             "blob": converters.dulwich_blob_to_content,
-            "blob2": converters.dulwich_blob_to_content_id,
             "tree": converters.dulwich_tree_to_directory,
             "commit": converters.dulwich_tree_to_directory,
             "tag": converters.dulwich_tag_to_release,
@@ -177,6 +203,17 @@
             with pytest.raises(ValueError):
                 _callable(Something())
 
+    def test_corrupt_tree(self):
+        # has a signature
+        sha1 = b"f0695c2e2fa7ce9d574023c3413761a473e500ca"
+        tree = copy.deepcopy(self.repo[sha1])
+        converters.dulwich_tree_to_directory(tree)
+
+        del tree._entries[next(iter(tree._entries))]
+
+        with pytest.raises(converters.HashMismatch):
+            converters.dulwich_tree_to_directory(tree)
+
     def test_commit_to_revision(self):
         sha1 = b"9768d0b576dbaaecd80abedad6dfd0d72f1476da"
 
@@ -251,6 +288,23 @@
 
         assert revision == expected_revision
 
+    @pytest.mark.parametrize(
+        "attribute", ["_message", "_encoding", "_author", "_gpgsig"]
+    )
+    def test_corrupt_commit(self, attribute):
+        # has a signature
+        sha1 = b"322f5bc915e50fc25e85226b5a182bded0e98e4b"
+        commit = copy.deepcopy(self.repo[sha1])
+        converters.dulwich_commit_to_revision(commit)
+        setattr(commit, attribute, b"abcde")
+        with pytest.raises(converters.HashMismatch):
+            converters.dulwich_commit_to_revision(commit)
+
+        if attribute == "_gpgsig":
+            setattr(commit, attribute, None)
+            with pytest.raises(converters.HashMismatch):
+                converters.dulwich_commit_to_revision(commit)
+
     def test_commit_to_revision_with_extra_headers_mergetag(self):
         sha1 = b"3ab3da4bf0f81407be16969df09cd1c8af9ac703"
 
@@ -319,9 +373,11 @@
             assert parsed_author == converters.parse_author(author)
 
     def test_dulwich_tag_to_release_no_author_no_date(self):
-        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf"
+        sha = hash_to_bytes("f6e367357b446bd1315276de5e88ba3d0d99e136")
+        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf7e25ce"
         message = b"some release message"
         tag = SWHTag(
+            sha=sha,
             name=b"blah",
             type_name=b"tag",
             target=target,
@@ -340,7 +396,7 @@
         expected_release = Release(
             author=None,
             date=None,
-            id=b"\xda9\xa3\xee^kK\r2U\xbf\xef\x95`\x18\x90\xaf\xd8\x07\t",
+            id=sha,
             message=message,
             metadata=None,
             name=b"blah",
@@ -352,8 +408,9 @@
         assert actual_release == expected_release
 
     def test_dulwich_tag_to_release_author_and_date(self):
+        sha = hash_to_bytes("fc1e6a4f1e37e93e28e78560e73efd0b12f616ef")
         tagger = b"hey dude <hello@mail.org>"
-        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf"
+        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf7e25ce"
         message = b"some release message"
 
         import datetime
@@ -361,6 +418,7 @@
         date = datetime.datetime(2007, 12, 5, tzinfo=datetime.timezone.utc).timestamp()
 
         tag = SWHTag(
+            sha=sha,
             name=b"blah",
             type_name=b"tag",
             target=target,
@@ -387,7 +445,7 @@
                 offset=0,
                 timestamp=Timestamp(seconds=1196812800, microseconds=0,),
             ),
-            id=b"\xda9\xa3\xee^kK\r2U\xbf\xef\x95`\x18\x90\xaf\xd8\x07\t",
+            id=sha,
             message=message,
             metadata=None,
             name=b"blah",
@@ -400,10 +458,12 @@
 
     def test_dulwich_tag_to_release_author_no_date(self):
         # to reproduce bug T815 (fixed)
+        sha = hash_to_bytes("41076e970975122dc6b2a878aa9797960bc4781d")
         tagger = b"hey dude <hello@mail.org>"
-        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf"
+        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf7e25ce"
         message = b"some release message"
         tag = SWHTag(
+            sha=sha,
             name=b"blah",
             type_name=b"tag",
             target=target,
@@ -426,7 +486,7 @@
                 name=b"hey dude",
             ),
             date=None,
-            id=b"\xda9\xa3\xee^kK\r2U\xbf\xef\x95`\x18\x90\xaf\xd8\x07\t",
+            id=sha,
             message=message,
             metadata=None,
             name=b"blah",
@@ -438,9 +498,11 @@
         assert actual_release == expected_release
 
     def test_dulwich_tag_to_release_signature(self):
-        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf"
+        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf7e25ce"
         message = b"some release message"
+        sha = hash_to_bytes("46fff489610ed733d2cc904e363070dadee05c71")
         tag = SWHTag(
+            sha=sha,
             name=b"blah",
             type_name=b"tag",
             target=target,
@@ -459,7 +521,7 @@
         expected_release = Release(
             author=None,
             date=None,
-            id=b"\xda9\xa3\xee^kK\r2U\xbf\xef\x95`\x18\x90\xaf\xd8\x07\t",
+            id=sha,
             message=message + GPGSIG,
             metadata=None,
             name=b"blah",
@@ -469,3 +531,32 @@
         )
 
         assert actual_release == expected_release
+
+    @pytest.mark.parametrize("attribute", ["name", "message", "signature"])
+    def test_corrupt_tag(self, attribute):
+        # has a signature
+        sha = hash_to_bytes("46fff489610ed733d2cc904e363070dadee05c71")
+        target = b"641fb6e08ddb2e4fd096dcf18e80b894bf7e25ce"
+        message = b"some release message"
+        tag = SWHTag(
+            sha=sha,
+            name=b"blah",
+            type_name=b"tag",
+            target=target,
+            target_type=b"commit",
+            message=message,
+            signature=GPGSIG,
+            tagger=None,
+            tag_time=None,
+            tag_timezone=None,
+        )
+        converters.dulwich_tag_to_release(tag)
+
+        setattr(tag, attribute, b"abcde")
+        with pytest.raises(converters.HashMismatch):
+            converters.dulwich_tag_to_release(tag)
+
+        if attribute == "signature":
+            setattr(tag, attribute, None)
+            with pytest.raises(converters.HashMismatch):
+                converters.dulwich_tag_to_release(tag)