--- a/hghooks/mozhghooks/check/prevent_subrepos.py
+++ b/hghooks/mozhghooks/check/prevent_subrepos.py
@@ -15,27 +15,16 @@ SUBREPO_NOT_ALLOWED = """
 
 Subrepositories are not allowed on this repository.
 
 Please remove .hgsub and/or .hgsubstate files from the repository and try your
 push again.
 """
 
 
-SUBREPO_WARNING = """
-{node} contains subrepositories.
-
-Subrepositories are an advanced Mercurial feature. Subrepositories are not
-allowed by default on non-user repositories. Attempting to push this changeset
-to a non-user repository on this server will result in rejection.
-
-Please consider not using subrepositories.
-"""
-
-
 class PreventSubReposCheck(PreTxnChangegroupCheck):
     """Prevents sub-repos from being committed.
 
     Sub-repos are a power user feature. They make it difficult to convert repos
     to and from Git. We also tend to prefer vendoring into a repo instead of
     creating a "symlink" to another repo.
 
     This check prevents the introduction of sub-repos on incoming changesets
@@ -45,33 +34,27 @@ class PreventSubReposCheck(PreTxnChangeg
     @property
     def name(self):
         return 'prevent_subrepos'
 
     def relevant(self):
         return True
 
     def pre(self):
-        self.fatal = not self.repo_metadata['user_repo']
         self.done = False
 
     def check(self, ctx):
         # Since the check can be non-fatal and since it requires a manifest
         # (which can be expensive to obtain), no-op if there is no work to do.
         if self.done:
             return True
 
         if '.hgsub' not in ctx and '.hgsubstate' not in ctx:
             return True
 
         self.done = True
 
-        if self.fatal:
-            print_banner(self.ui, 'error', SUBREPO_NOT_ALLOWED.format(
-                node=ctx.hex()[0:12]))
-            return False
-        else:
-            print_banner(self.ui, 'warning', SUBREPO_WARNING.format(
-                node=ctx.hex()[0:12]))
-            return True
+        print_banner(self.ui, 'error', SUBREPO_NOT_ALLOWED.format(
+            node=ctx.hex()[0:12]))
+        return False
 
     def post_check(self):
         return True

--- a/hghooks/tests/test-prevent-subrepos.t
+++ b/hghooks/tests/test-prevent-subrepos.t
@@ -1,11 +1,11 @@
   $ . $TESTDIR/hghooks/tests/common.sh
 
-We can create subrepos on user repos (but a warning is printed)
+We cannot create subrepos on user repos (but a warning is printed)
 
   $ mkdir -p users/someuser
   $ hg init users/someuser/repo
   $ hg init users/someuser/repo/subrepo
   $ configurehooks users/someuser/repo
 
   $ hg -q clone users/someuser/repo client
   $ cd client
@@ -37,26 +37,29 @@ We can create subrepos on user repos (bu
   pushing subrepo mysubrepo to $TESTTMP/users/someuser/repo/subrepo
   no changes found
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 2 changes to 2 files
   
-  ********************************** WARNING ***********************************
+  *********************************** ERROR ************************************
   5e42dc5815d5 contains subrepositories.
   
-  Subrepositories are an advanced Mercurial feature. Subrepositories are not
-  allowed by default on non-user repositories. Attempting to push this changeset
-  to a non-user repository on this server will result in rejection.
+  Subrepositories are not allowed on this repository.
   
-  Please consider not using subrepositories.
+  Please remove .hgsub and/or .hgsubstate files from the repository and try your
+  push again.
   ******************************************************************************
   
+  transaction abort!
+  rollback completed
+  abort: pretxnchangegroup.mozhooks hook failed
+  [255]
   $ cd ..
 
 We cannot create subrepos on non-user repos
 
   $ hg init server
   $ configurehooks server
 We need this to exist so sub-repo push works
   $ hg init server/subrepo