diff --git a/src/escpos/printer/lp.py b/src/escpos/printer/lp.py
index e0824e4..3d9440b 100644
--- a/src/escpos/printer/lp.py
+++ b/src/escpos/printer/lp.py
@@ -145,7 +145,7 @@ class LP(Escpos):
                 return
         logging.info("LP printer enabled")
 
-    def close(self):
+    def close(self) -> None:
         """Stop the subprocess."""
         if not self._device:
             return