diff --git a/CHANGES.md b/CHANGES.md
index c5887e7..134e616 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,11 +2,8 @@
 
 ## [Unreleased]
 
-<<<<<<< HEAD
 - Enable filter extension for `GET /items` requests and add `Queryables` links in `/collections` and `/collections/{collection_id}` responses ([#89](https://github.com/stac-utils/stac-fastapi-pgstac/pull/89))
-=======
 - Add collection search extension
->>>>>>> 9b2050a (add collection search extension)
 
 ## [3.0.0a4] - 2024-07-10
 
diff --git a/stac_fastapi/pgstac/core.py b/stac_fastapi/pgstac/core.py
index ba85916..d6aeb1e 100644
--- a/stac_fastapi/pgstac/core.py
+++ b/stac_fastapi/pgstac/core.py
@@ -2,7 +2,7 @@
 
 import re
 from typing import Any, Dict, List, Optional, Set, Union
-from urllib.parse import unquote_plus
+from urllib.parse import unquote_plus, urljoin
 
 import attr
 import orjson
@@ -17,11 +17,12 @@
 from stac_fastapi.extensions.core.collection_search.request import (
     BaseCollectionSearchPostRequest,
 )
-from stac_fastapi.types.core import AsyncBaseCoreClient
+from stac_fastapi.types.core import AsyncBaseCoreClient, Relations
 from stac_fastapi.types.errors import InvalidQueryParameter, NotFoundError
+from stac_fastapi.types.requests import get_base_url
 from stac_fastapi.types.rfc3339 import DateTimeType
 from stac_fastapi.types.stac import Collection, Collections, Item, ItemCollection
-from stac_pydantic.shared import BBox
+from stac_pydantic.shared import BBox, MimeTypes
 
 from stac_fastapi.pgstac.config import Settings
 from stac_fastapi.pgstac.models.links import (
@@ -111,7 +112,7 @@ async def _collection_search_base(  # noqa: C901
         Returns:
             All collections which match the search criteria.
         """
-
+        base_url = get_base_url(request)
         search_request_json = search_request.model_dump_json(
             exclude_none=True, by_alias=True
         )