diff --git a/nextcloud_mcp_server/client/contacts.py b/nextcloud_mcp_server/client/contacts.py
index ae0aef81..f4eb1678 100644
--- a/nextcloud_mcp_server/client/contacts.py
+++ b/nextcloud_mcp_server/client/contacts.py
@@ -258,7 +258,7 @@ class ContactsClient(BaseNextcloudClient):
     async def _resolve_object_name(self, addressbook: str, uid: str) -> str | None:
         """Map a surfaced contact id back to its real CardDAV object filename.
 
-        ``list_contacts`` surfaces ``vcard_id`` with any ``.vcf`` suffix
+        ``list_contacts`` surfaces ``vcard_id`` with a trailing ``.vcf`` suffix
         stripped, so reverse that transform here: return the object whose
         filename reduces to ``uid``. The conventional ``<uid>.vcf`` is
         preferred when present (deterministic for the common case), otherwise
@@ -267,7 +267,7 @@ class ContactsClient(BaseNextcloudClient):
         candidates = [
             name
             for name in await self._list_object_names(addressbook)
-            if name.replace(".vcf", "") == uid
+            if name.removesuffix(".vcf") == uid
         ]
         if not candidates:
             return None
@@ -512,7 +512,9 @@ class ContactsClient(BaseNextcloudClient):
                 continue
             # ``vcard_id`` keeps the historical ``.vcf``-stripped form for
             # backward compatibility with callers that use it as the contact id.
-            vcard_id = object_name.replace(".vcf", "")
+            # Must use the same trailing-suffix strip as ``_resolve_object_name``
+            # so the surface-then-resolve round-trip stays lossless (issue #874).
+            vcard_id = object_name.removesuffix(".vcf")
 
             # Get properties
             propstat = response_elem.find(".//d:propstat", ns)
diff --git a/tests/unit/client/test_contacts.py b/tests/unit/client/test_contacts.py
index c95de897..d332e455 100644
--- a/tests/unit/client/test_contacts.py
+++ b/tests/unit/client/test_contacts.py
@@ -296,6 +296,55 @@ class TestObjectNameResolution:
             "/remote.php/dav/addressbooks/users/testuser/contacts/ghost.vcf",
         )
 
+    async def test_update_targets_real_no_extension_path(self, mocker):
+        """Regression for #874: update must PUT to ``.../default`` not
+        ``.../default.vcf`` (parallels the delete coverage).
+        """
+        client = ContactsClient.__new__(ContactsClient)
+        client.username = "testuser"
+        mocker.patch.object(
+            client, "_resolve_object_name", mocker.AsyncMock(return_value="default")
+        )
+        mocker.patch.object(
+            client,
+            "_fetch_raw_vcard",
+            mocker.AsyncMock(
+                return_value=(
+                    "BEGIN:VCARD\nVERSION:3.0\nUID:default\nFN:No Ext\nEND:VCARD\n",
+                    '"etag"',
+                )
+            ),
+        )
+        make_request = mocker.patch.object(client, "_make_request", mocker.AsyncMock())
+        await client.update_contact(
+            addressbook="contacts", uid="default", contact_data={"fn": "Updated"}
+        )
+        method, url = make_request.await_args.args[0], make_request.await_args.args[1]
+        assert method == "PUT"
+        assert url == "/remote.php/dav/addressbooks/users/testuser/contacts/default"
+
+    async def test_update_falls_back_to_vcf_when_unresolved(self, mocker):
+        """When resolution finds nothing, update falls back to ``<uid>.vcf`` so
+        the caller still gets a clean 404 from the PUT (mirrors delete).
+        """
+        client = ContactsClient.__new__(ContactsClient)
+        client.username = "testuser"
+        mocker.patch.object(
+            client, "_resolve_object_name", mocker.AsyncMock(return_value=None)
+        )
+        make_request = mocker.patch.object(client, "_make_request", mocker.AsyncMock())
+        # Supplying an etag skips the existing-vCard fetch; update builds a fresh
+        # vCard and PUTs it to the fallback path.
+        await client.update_contact(
+            addressbook="contacts",
+            uid="ghost",
+            contact_data={"fn": "Ghost"},
+            etag='"x"',
+        )
+        method, url = make_request.await_args.args[0], make_request.await_args.args[1]
+        assert method == "PUT"
+        assert url == "/remote.php/dav/addressbooks/users/testuser/contacts/ghost.vcf"
+
 
 class TestFirstCustom:
     """``_first_custom`` is the read-side companion to PR #719 — it pulls