diff --git a/error.py b/error.py
index 7958a0a1..36bc2129 100644
--- a/error.py
+++ b/error.py
@@ -107,6 +107,10 @@ class GitError(RepoError):
         return self.message
 
 
+class GitAuthError(RepoExitError):
+    """Cannot talk to remote due to auth issue."""
+
+
 class GitcUnsupportedError(RepoExitError):
     """Gitc no longer supported."""
 
diff --git a/project.py b/project.py
index b29e604f..88dd747b 100644
--- a/project.py
+++ b/project.py
@@ -32,6 +32,7 @@ import urllib.parse
 
 from color import Coloring
 from error import DownloadError
+from error import GitAuthError
 from error import GitError
 from error import ManifestInvalidPathError
 from error import ManifestInvalidRevisionError
@@ -2713,6 +2714,20 @@ class Project:
                     file=output_redir,
                 )
                 break
+            elif (
+                ret == 128
+                and gitcmd.stdout
+                and "remote helper 'sso' aborted session" in gitcmd.stdout
+            ):
+                # User needs to be authenticated, and Git wants to prompt for
+                # username and password.
+                print(
+                    "git requires authentication, but repo cannot perform "
+                    "interactive authentication.",
+                    file=output_redir,
+                )
+                raise GitAuthError(gitcmd.stdout)
+                break
             elif current_branch_only and is_sha1 and ret == 128:
                 # Exit code 128 means "couldn't find the ref you asked for"; if
                 # we're in sha1 mode, we just tried sync'ing from the upstream