diff --git a/r2/r2/controllers/api.py b/r2/r2/controllers/api.py
index ea7afd4d3..9b7ccf4ba 100644
--- a/r2/r2/controllers/api.py
+++ b/r2/r2/controllers/api.py
@@ -1457,6 +1457,9 @@ class ApiController(RedditController):
                                   subreddit=thing.subreddit_slow.name):
             abort(404, 'not found')
 
+        if thing.archived:
+            return abort(400, "Bad Request")
+
         thing.locked = True
         thing._commit()
 
@@ -1480,6 +1483,9 @@ class ApiController(RedditController):
                                   subreddit=thing.subreddit_slow.name):
             abort(404, 'not found')
 
+        if thing.archived:
+            return abort(400, "Bad Request")
+
         thing.locked = False
         thing._commit()
 
diff --git a/r2/r2/lib/pages/things.py b/r2/r2/lib/pages/things.py
index 056ac6aae..d3416c838 100644
--- a/r2/r2/lib/pages/things.py
+++ b/r2/r2/lib/pages/things.py
@@ -97,8 +97,9 @@ class LinkButtons(PrintableButtons):
         editable = is_author and thing_editable and not thing_takendown
 
         show_lock = show_unlock = False
-        if thing.can_ban and feature.is_enabled('thread_locking',
-                                                subreddit=thing.subreddit.name):
+        lockable = thing.can_ban and not thing.archived
+        if (lockable and feature.is_enabled('thread_locking',
+                                            subreddit=thing.subreddit.name)):
             show_lock = not thing.locked
             show_unlock = not show_lock