diff --git a/plugins/views_plugin_display.inc b/plugins/views_plugin_display.inc
index 59bec3b4aa2c21a36d8146ac16290dcb5aeb8e3d..431277825ad58bb9f3682993e3efde52a5baf23c 100644
--- a/plugins/views_plugin_display.inc
+++ b/plugins/views_plugin_display.inc
@@ -985,7 +985,8 @@ function get_field_labels() {
     // Use func_get_arg so the function signature isn't amended
     // but we can still pass TRUE into the function to filter
     // by groupable handlers.
-    $groupable_only = func_get_arg(0);
+    $args = func_get_args();
+    $groupable_only = isset($args[0]) ? $args[0] : FALSE;
 
     $options = array();
     foreach ($this->get_handlers('relationship') as $relationship => $handler) {