diff --git a/src/mapi/glapi/gen/gl_XML.py b/src/mapi/glapi/gen/gl_XML.py
index 94e742f7b9b..da80ea1b860 100644
--- a/src/mapi/glapi/gen/gl_XML.py
+++ b/src/mapi/glapi/gen/gl_XML.py
@@ -653,6 +653,12 @@ class gl_function( gl_item ):
         name = element.get( "name" )
         alias = element.get( "alias" )
 
+        # marshal isn't allowed with alias
+        assert not alias or not element.get('marshal')
+        assert not alias or not element.get('marshal_count')
+        assert not alias or not element.get('marshal_sync')
+        assert not alias or not element.get('marshal_call_after')
+
         if name in static_data.functions:
             self.static_entry_points.append(name)