diff --git a/beetsplug/musicbrainz.py b/beetsplug/musicbrainz.py
index 8e259e94b..772972c07 100644
--- a/beetsplug/musicbrainz.py
+++ b/beetsplug/musicbrainz.py
@@ -29,7 +29,7 @@ from confuse.exceptions import NotFoundError
 
 import beets
 import beets.autotag.hooks
-from beets import config, plugins, util
+from beets import config, importer, plugins, util
 from beets.metadata_plugins import MetadataSourcePlugin
 from beets.util.id_extractors import extract_release_id
 
@@ -55,6 +55,26 @@ FIELDS_TO_MB_KEYS = {
     "year": "date",
 }
 
+_MB_REIMPORT_FRESH_FIELDS_ALBUM = [
+    "media",
+    "releasegroup_id",
+    "data_url",
+]
+_MB_REIMPORT_FRESH_FIELDS_ITEM = [
+    "data_url",
+]
+
+
+def _extend_reimport_fresh_fields() -> None:
+    """Ensure MusicBrainz fields stored as flex attrs refresh on reimport."""
+    for field in _MB_REIMPORT_FRESH_FIELDS_ALBUM:
+        if field not in importer.REIMPORT_FRESH_FIELDS_ALBUM:
+            importer.REIMPORT_FRESH_FIELDS_ALBUM.append(field)
+    for field in _MB_REIMPORT_FRESH_FIELDS_ITEM:
+        if field not in importer.REIMPORT_FRESH_FIELDS_ITEM:
+            importer.REIMPORT_FRESH_FIELDS_ITEM.append(field)
+
+
 musicbrainzngs.set_useragent("beets", beets.__version__, "https://beets.io/")
 
 
@@ -367,6 +387,7 @@ class MusicBrainzPlugin(MetadataSourcePlugin):
         from the beets configuration. This should be called at startup.
         """
         super().__init__()
+        _extend_reimport_fresh_fields()
         self.config.add(
             {
                 "host": "musicbrainz.org",
diff --git a/docs/changelog.rst b/docs/changelog.rst
index e74f0caa2..74093596e 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -19,6 +19,8 @@ New features:
 
 Bug fixes:
 
+- :doc:`plugins/musicbrainz` Refresh flexible MusicBrainz metadata on reimport
+  so format changes are applied. :bug:`6036`
 - :doc:`plugins/spotify` Ensure ``spotifysync`` keeps popularity, ISRC, and
   related fields current even when audio features requests fail. :bug:`6061`
 - :doc:`plugins/spotify` Fixed an issue where track matching and lookups could