diff --git a/addon_imps/storage/owncloud.py b/addon_imps/storage/owncloud.py
index 70b0e77f..832b3c5b 100644
--- a/addon_imps/storage/owncloud.py
+++ b/addon_imps/storage/owncloud.py
@@ -63,6 +63,7 @@ async def get_external_account_id(self, auth_result_extras: dict[str, str]) -> s
             response_xml = await response.text_content()
             return self._parse_displayname(response_xml)
 
+    @property
     def _fallback_username(self) -> str | None:
         return "default-username"
 
diff --git a/addon_service/common/waterbutler_compat.py b/addon_service/common/waterbutler_compat.py
index cb2e8988..f6d59ab1 100644
--- a/addon_service/common/waterbutler_compat.py
+++ b/addon_service/common/waterbutler_compat.py
@@ -22,14 +22,27 @@ class JSONAPIMeta:
     credentials = serializers.SerializerMethodField("_credentials_for_waterbutler")
     config = serializers.SerializerMethodField("_config_for_waterbutler")
 
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._wb_config_cache = {}
+
+    def _get_wb_config(self, configured_storage_addon):
+        cache_key = configured_storage_addon.id
+        if cache_key in self._wb_config_cache:
+            return self._wb_config_cache[cache_key]
+        else:
+            imp = get_storage_addon_instance__blocking(
+                configured_storage_addon.imp_cls,
+                configured_storage_addon.base_account,
+                configured_storage_addon.config,
+            )
+            wb_config = async_to_sync(imp.build_wb_config)()
+            self._wb_config_cache[cache_key] = wb_config
+            return wb_config
+
     def _credentials_for_waterbutler(self, configured_storage_addon):
         _creds_data = configured_storage_addon.credentials
-        imp = get_storage_addon_instance__blocking(
-            configured_storage_addon.imp_cls,
-            configured_storage_addon.base_account,
-            configured_storage_addon.config,
-        )
-        wb_config = async_to_sync(imp.build_wb_config)()
+        wb_config = self._get_wb_config(configured_storage_addon)
 
         match type(_creds_data):
             case credentials.AccessTokenCredentials:
@@ -50,10 +63,5 @@ def _credentials_for_waterbutler(self, configured_storage_addon):
                 raise ValueError(f"unknown credentials type: {_creds_data}")
 
     def _config_for_waterbutler(self, configured_storage_addon: ConfiguredStorageAddon):
-        imp = get_storage_addon_instance__blocking(
-            configured_storage_addon.imp_cls,
-            configured_storage_addon.base_account,
-            configured_storage_addon.config,
-        )
-        wb_config = async_to_sync(imp.build_wb_config)()
+        wb_config = self._get_wb_config(configured_storage_addon)
         return wb_config