diff --git a/scripts/register_new_matrix_user b/scripts/register_new_matrix_user
index 27a6250b1..6d055fd01 100755
--- a/scripts/register_new_matrix_user
+++ b/scripts/register_new_matrix_user
@@ -25,12 +25,17 @@ import urllib2
 import yaml
 
 
-def request_registration(user, password, server_location, shared_secret):
+def request_registration(user, password, server_location, shared_secret, admin=False):
     mac = hmac.new(
         key=shared_secret,
-        msg=user,
         digestmod=hashlib.sha1,
-    ).hexdigest()
+    )
+
+    mac.update(user)
+    mac.update(password)
+    mac.update("admin" if admin else "notadmin")
+
+    mac = mac.hexdigest()
 
     data = {
         "user": user,
diff --git a/synapse/rest/client/v1/register.py b/synapse/rest/client/v1/register.py
index d791d5e07..0eb7490e5 100644
--- a/synapse/rest/client/v1/register.py
+++ b/synapse/rest/client/v1/register.py
@@ -324,6 +324,8 @@ class RegisterRestServlet(ClientV1RestServlet):
             raise SynapseError(400, "Shared secret registration is not enabled")
 
         user = register_json["user"].encode("utf-8")
+        password = register_json["password"].encode("utf-8")
+        admin = register_json.get("admin", None)
 
         # str() because otherwise hmac complains that 'unicode' does not
         # have the buffer interface
@@ -331,11 +333,12 @@ class RegisterRestServlet(ClientV1RestServlet):
 
         want_mac = hmac.new(
             key=self.hs.config.registration_shared_secret,
-            msg=user,
             digestmod=sha1,
-        ).hexdigest()
-
-        password = register_json["password"].encode("utf-8")
+        )
+        want_mac.update(user)
+        want_mac.update(password)
+        want_mac.update("admin" if admin else "notadmin")
+        want_mac = want_mac.hexdigest()
 
         if compare_digest(want_mac, got_mac):
             handler = self.handlers.registration_handler