diff --git a/backup/backup.py b/backup/backup.py
index 6459572..624e27b 100644
--- a/backup/backup.py
+++ b/backup/backup.py
@@ -112,15 +112,17 @@ class Backup(commands.Cog):
                     repo_e.append(f"Repository {name} already exists.")
                     continue
 
-                except errors.AuthenticationError as err:
-                    repo_e.append(f"Authentication error while adding repository {name}. See logs for more information.")
-                    self.log.exception(
-                        "Something went wrong whilst cloning %s (to revision %s)",
-                        url,
-                        branch,
-                        exc_info=err,
-                    )
-                    continue
+                # This is commented out because errors.AuthenticationError is not yet implemented in Red 3.5.5's Downloader cog.
+                # Rather, it is only in the development version and will be added in version 3.5.6 (or whatever the next version is).
+                # except errors.AuthenticationError as err:
+                #     repo_e.append(f"Authentication error while adding repository {name}. See logs for more information.")
+                #     self.log.exception(
+                #         "Something went wrong whilst cloning %s (to revision %s)",
+                #         url,
+                #         branch,
+                #         exc_info=err,
+                #     )
+                #     continue
 
                 except errors.CloningError as err:
                     repo_e.append(f"Cloning error while adding repository {name}. See logs for more information.")