diff --git a/plugins/Authentication/AuthenticationPlugin.php b/plugins/Authentication/AuthenticationPlugin.php
index a80da901cf..1b9084187b 100644
--- a/plugins/Authentication/AuthenticationPlugin.php
+++ b/plugins/Authentication/AuthenticationPlugin.php
@@ -204,7 +204,7 @@ abstract class AuthenticationPlugin extends Plugin
 
     function onCheckSchema() {
         $schema = Schema::get();
-        $schema->ensureDataObject(User_username);
+        $schema->ensureDataObject('User_username');
         return true;
     }
 
diff --git a/plugins/OpenID/OpenIDPlugin.php b/plugins/OpenID/OpenIDPlugin.php
index 88e23ea3e5..6dd8a3f5a3 100644
--- a/plugins/OpenID/OpenIDPlugin.php
+++ b/plugins/OpenID/OpenIDPlugin.php
@@ -281,8 +281,8 @@ class OpenIDPlugin extends Plugin
 
     function onCheckSchema() {
         $schema = Schema::get();
-        $schema->ensureDataObject(User_openid);
-        $schema->ensureDataObject(User_openid_trustroot);
+        $schema->ensureDataObject('User_openid');
+        $schema->ensureDataObject('User_openid_trustroot');
         return true;
     }
 
diff --git a/plugins/UserFlag/UserFlagPlugin.php b/plugins/UserFlag/UserFlagPlugin.php
index df7eac7a2b..b4d48c74bc 100644
--- a/plugins/UserFlag/UserFlagPlugin.php
+++ b/plugins/UserFlag/UserFlagPlugin.php
@@ -48,7 +48,7 @@ class UserFlagPlugin extends Plugin
         $schema = Schema::get();
 
         // For storing user-submitted flags on profiles
-        $schema->ensureDataObject(User_flag_profile);
+        $schema->ensureDataObject('User_flag_profile');
 
         return true;
     }