diff --git a/plugins/sudoers/sudoers.c b/plugins/sudoers/sudoers.c
index 6c4b27f48..f9a9bb466 100644
--- a/plugins/sudoers/sudoers.c
+++ b/plugins/sudoers/sudoers.c
@@ -1314,6 +1314,8 @@ deserialize_info(char * const settings[], char * const user_info[])
 	    continue;
 	}
     }
+    if (user_tty == NULL)
+	user_tty = "unknown"; /* user_ttypath remains NULL */
 
 #undef MATCHES
     return flags;