diff --git a/synapse/rest/admin/users.py b/synapse/rest/admin/users.py

index f39e3d6d5c..68c3c64a0d 100644
--- a/synapse/rest/admin/users.py
+++ b/synapse/rest/admin/users.py
@@ -83,17 +83,32 @@ class UsersRestServletV2(RestServlet):
     The parameter `deactivated` can be used to include deactivated users.
     """
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.store = hs.get_datastore()
         self.auth = hs.get_auth()
         self.admin_handler = hs.get_admin_handler()
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         await assert_requester_is_admin(self.auth, request)
 
         start = parse_integer(request, "from", default=0)
         limit = parse_integer(request, "limit", default=100)
+
+        if start < 0:
+            raise SynapseError(
+                400,
+                "Query parameter from must be a string representing a positive integer.",
+                errcode=Codes.INVALID_PARAM,
+            )
+
+        if limit < 0:
+            raise SynapseError(
+                400,
+                "Query parameter limit must be a string representing a positive integer.",
+                errcode=Codes.INVALID_PARAM,
+            )
+
         user_id = parse_string(request, "user_id", default=None)
         name = parse_string(request, "name", default=None)
         guests = parse_boolean(request, "guests", default=True)
@@ -103,7 +118,7 @@ class UsersRestServletV2(RestServlet):
             start, limit, user_id, name, guests, deactivated
         )
         ret = {"users": users, "total": total}
-        if len(users) >= limit:
+        if (start + limit) < total:
             ret["next_token"] = str(start + len(users))
 
         return 200, ret
@@ -875,3 +890,39 @@ class UserTokenRestServlet(RestServlet):
         )
 
         return 200, {"access_token": token}
+
+
+class ShadowBanRestServlet(RestServlet):
+    """An admin API for shadow-banning a user.
+
+    A shadow-banned users receives successful responses to their client-server
+    API requests, but the events are not propagated into rooms.
+
+    Shadow-banning a user should be used as a tool of last resort and may lead
+    to confusing or broken behaviour for the client.
+
+    Example:
+
+        POST /_synapse/admin/v1/users/@test:example.com/shadow_ban
+        {}
+
+        200 OK
+        {}
+    """
+
+    PATTERNS = admin_patterns("/users/(?P<user_id>[^/]*)/shadow_ban")
+
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+        self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
+
+    async def on_POST(self, request, user_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        if not self.hs.is_mine_id(user_id):
+            raise SynapseError(400, "Only local users can be shadow-banned")
+
+        await self.store.set_shadow_banned(UserID.from_string(user_id), True)
+
+        return 200, {}