diff --git a/data/registry_model/registry_proxy_model.py b/data/registry_model/registry_proxy_model.py
index b6e666390..9cfb36e6d 100644
--- a/data/registry_model/registry_proxy_model.py
+++ b/data/registry_model/registry_proxy_model.py
@@ -315,14 +315,24 @@ class ProxyModel(OCIModel):
         freshly out of the database, and a boolean indicating whether the returned
         tag was newly created or not.
         """
+        upstream_manifest = None
         upstream_digest = self._proxy.manifest_exists(manifest_ref, ACCEPTED_MEDIA_TYPES)
         up_to_date = manifest.digest == upstream_digest
+
+        # manifest_exists will return an empty/None digest when the upstream
+        # registry omits the docker-content-digest header.
+        if not upstream_digest:
+            upstream_manifest = self._pull_upstream_manifest(repo_ref.name, manifest_ref)
+            up_to_date = manifest.digest == upstream_manifest.digest
+
         placeholder = manifest.internal_manifest_bytes.as_unicode() == ""
         if up_to_date and not placeholder:
             return tag, False
 
+        if upstream_manifest is None:
+            upstream_manifest = self._pull_upstream_manifest(repo_ref.name, manifest_ref)
+
         self._enforce_repository_quota(repo_ref)
-        upstream_manifest = self._pull_upstream_manifest(repo_ref.name, manifest_ref)
         if up_to_date and placeholder:
             with db_disallow_replica_use():
                 with db_transaction():
diff --git a/proxy/__init__.py b/proxy/__init__.py
index 776ba49d9..1c0e6790a 100644
--- a/proxy/__init__.py
+++ b/proxy/__init__.py
@@ -79,8 +79,10 @@ class Proxy:
 
     def manifest_exists(self, image_ref: str, media_types: list[str] | None = None) -> str | None:
         """
-        Returns the manifest digest (docker-content-digest) if given by the
-        upstream registry.
+        Returns the manifest digest.
+
+        Looks for the digest in the docker-content-digest header. If not
+        present in the response, parses the manifest then calculate the digest.
 
         If the manifest does not exist or the upstream registry errors, raises
         an UpstreamRegistryError exception.
@@ -96,6 +98,9 @@ class Proxy:
         url = f"{self.base_url}/v2/{self._repo}/blobs/{digest}"
         resp = self.get(
             url,
+            headers={
+                "Accept-Encoding": "identity",
+            },
             allow_redirects=True,
             stream=True,
         )
diff --git a/proxy/test_proxy.py b/proxy/test_proxy.py
index a2789a949..75294d972 100644
--- a/proxy/test_proxy.py
+++ b/proxy/test_proxy.py
@@ -18,6 +18,7 @@ ANONYMOUS_TOKEN = "anonymous-token"
 USER_TOKEN = "user-token"
 TAG = "14"
 TAG_404 = "666"
+TAG_NO_DIGEST = "11"
 DIGEST = "sha256:2e7d2c03a9507ae265ecf5b5356885a53393a2029d241394997265a1a25aefc6"
 DIGEST_404 = "sha256:3e23e8160039594a33894f6564e1b1348bbd7a0088d42c4acb73eeaed59c009d"
 
@@ -119,7 +120,11 @@ def docker_registry_manifest(url, request):
             }
         ],
     }
-    return response(200, content, request=request)
+    headers = {
+        "docker-content-digest": DIGEST,
+        "content-type": "application/vnd.docker.distribution.manifest.v2+json",
+    }
+    return response(200, content, headers, request=request)
 
 
 def docker_registry_manifest_404(url, request):
@@ -135,6 +140,10 @@ def docker_registry_manifest_404(url, request):
     return response(404, content, request=request)
 
 
+def docker_registry_manifest_no_digest(url, request):
+    return response(200, "", request=request)
+
+
 def docker_registry_blob(url, request):
     return response(200, request=request)
 
@@ -160,6 +169,9 @@ def docker_registry_mock(url, request):
         elif url.path == f"/v2/library/postgres/manifests/{TAG_404}":
             return docker_registry_manifest_404(url, request)
 
+        elif url.path == f"/v2/library/postgres/manifests/{TAG_NO_DIGEST}":
+            return docker_registry_manifest_no_digest(url, request)
+
         elif url.path == f"/v2/library/postgres/blobs/{DIGEST}":
             return docker_registry_blob(url, request)
 
@@ -312,6 +324,7 @@ class TestProxy(unittest.TestCase):
             proxy = Proxy(self.config, "library/postgres")
             digest = proxy.manifest_exists(image_ref=TAG)
         self.assertNotEqual(digest, "")
+        self.assertNotEqual(digest, None)
 
     def test_manifest_exists_404(self):
         with HTTMock(docker_registry_mock):
@@ -321,6 +334,12 @@ class TestProxy(unittest.TestCase):
 
         self.assertIn("404", str(excinfo.value))
 
+    def test_manifest_exists_without_digest_header(self):
+        with HTTMock(docker_registry_mock):
+            proxy = Proxy(self.config, "library/postgres")
+            digest = proxy.manifest_exists(image_ref=TAG_NO_DIGEST)
+        self.assertIsNone(digest, None)
+
     def test_get_blob(self):
         with HTTMock(docker_registry_mock):
             proxy = Proxy(self.config, "library/postgres")