diff --git a/src/borg/testsuite/platform.py b/src/borg/testsuite/platform.py
index 183e10a08..0001eeecd 100644
--- a/src/borg/testsuite/platform.py
+++ b/src/borg/testsuite/platform.py
@@ -40,7 +40,7 @@ def user_exists(username):
     try:
         pwd.getpwnam(username)
         return True
-    except KeyError:
+    except (KeyError, ValueError):
         return False