diff --git a/proto/ei-scanner b/proto/ei-scanner
index dd60ea7..aabebee 100755
--- a/proto/ei-scanner
+++ b/proto/ei-scanner
@@ -789,6 +789,7 @@ def generate_source(
     data["interfaces"] = proto.interfaces
     data["extra"] = extra_data
 
+    loader: jinja2.BaseLoader
     if template == "-":
         loader = jinja2.FunctionLoader(lambda _: sys.stdin.read())
         filename = "<stdin>"
@@ -913,17 +914,17 @@ def main() -> None:
 
         extra_data = json.loads(ns.jinja_extra_data)
     elif ns.jinja_extra_data_file is not None:
-        if ns.jinja_extra_data.name.endswith(
+        if ns.jinja_extra_data_file.name.endswith(
             ".yml"
-        ) or ns.jinja_extra_data.name.endswith(".yaml"):
+        ) or ns.jinja_extra_data_file.name.endswith(".yaml"):
             import yaml
 
-            with open(ns.jinja_extra_data) as fd:
+            with open(ns.jinja_extra_data_file) as fd:
                 extra_data = yaml.safe_load(fd)
-        elif ns.jinja_extra_data.name.endswith(".json"):
+        elif ns.jinja_extra_data_file.name.endswith(".json"):
             import json
 
-            with open(ns.jinja_extra_data) as fd:
+            with open(ns.jinja_extra_data_file) as fd:
                 extra_data = json.load(fd)
         else:
             print("Unknown file format for jinja data", file=sys.stderr)