diff --git a/midas/checker/checker.py b/midas/checker/checker.py
index aff3782..dcf90b0 100644
--- a/midas/checker/checker.py
+++ b/midas/checker/checker.py
@@ -232,30 +232,37 @@ class Checker(
                 return arg.default.accept(self)
             return UnknownType()
 
+        pos: int = 0
         for arg in stmt.posonlyargs:
             pos_args.append(
                 Function.Argument(
+                    pos=pos,
                     name=arg.name,
                     type=eval_arg_type(arg),
                     required=arg.default is None,
                 )
             )
+            pos += 1
         for arg in stmt.args:
             args.append(
                 Function.Argument(
+                    pos=pos,
                     name=arg.name,
                     type=eval_arg_type(arg),
                     required=arg.default is None,
                 )
             )
+            pos += 1
         for arg in stmt.kwonlyargs:
             kw_args.append(
                 Function.Argument(
+                    pos=pos,  # not relevant
                     name=arg.name,
                     type=eval_arg_type(arg),
                     required=arg.default is None,
                 )
             )
+            pos += 1
 
         for arg in pos_args + args + kw_args:
             env.define(arg.name, arg.type)
diff --git a/midas/checker/types.py b/midas/checker/types.py
index d62c867..c1d4449 100644
--- a/midas/checker/types.py
+++ b/midas/checker/types.py
@@ -34,6 +34,7 @@ class Function:
 
     @dataclass(frozen=True, kw_only=True)
     class Argument:
+        pos: int
         name: str
         type: Type
         required: bool