diff --git a/tools/spec.py b/tools/spec.py
index 6b715fc..99e04f8 100644
--- a/tools/spec.py
+++ b/tools/spec.py
@@ -716,7 +716,7 @@ def parse_extensions(reg:registry, root):
 
 
 ###############################################################################
-def write_header(path:str, q):
+def write_header(path:str, q:List[type]):
     with open(path, 'w') as dst:
         dst.write("#pragma once\n")
 
@@ -768,7 +768,7 @@ def write_header(path:str, q):
 
 
 ##-----------------------------------------------------------------------------
-def write_icd(path:str, q):
+def write_icd(path:str, q:List[type]):
     with open(path, 'w') as icd:
         commands = [i for i in q if isinstance(i, command)]
         instance_commands = [i for i in commands if i.is_instance(reg)]
@@ -815,7 +815,7 @@ def write_icd(path:str, q):
 
 
 ##-----------------------------------------------------------------------------
-def write_dispatch(path:str, q):
+def write_dispatch(path:str, q:List[type]):
     with open(path, 'w') as dispatch:
         dispatch.write("""
         #include "../vk.hpp"