diff --git a/src/ukify/ukify.py b/src/ukify/ukify.py
index caa9a04000..06967b02b9 100755
--- a/src/ukify/ukify.py
+++ b/src/ukify/ukify.py
@@ -467,7 +467,7 @@ class SignTool:
         raise NotImplementedError()
 
     @staticmethod
-    def from_string(name) -> type['SignTool']:
+    def from_string(name: str) -> type['SignTool']:
         if name == 'pesign':
             return PeSign
         elif name == 'sbsign':