diff --git a/src/escpos/cli.py b/src/escpos/cli.py
index e7cc826..f70d922 100644
--- a/src/escpos/cli.py
+++ b/src/escpos/cli.py
@@ -20,7 +20,7 @@ except ImportError:
     pass  # noqa
 import sys
 
-from . import config
+from . import config, escpos
 from . import printer as escpos_printer_module
 from . import version
 
@@ -617,7 +617,7 @@ def main() -> None:
         globals()[target_command](**command_arguments)
 
 
-def demo(printer, **kwargs) -> None:
+def demo(printer: escpos.Escpos, **kwargs) -> None:
     """Print demos.
 
     Called when CLI is passed `demo`. This function
diff --git a/test/test_raise_arbitrary_error.py b/test/test_raise_arbitrary_error.py
index 475dc02..07ad76e 100644
--- a/test/test_raise_arbitrary_error.py
+++ b/test/test_raise_arbitrary_error.py
@@ -23,7 +23,7 @@ def test_raise_error_wrongly():
         raise escpos.Error("This should raise an AttributeError.")
 
 
-def tests_raise_error():
+def tests_raise_error() -> None:
     """raise error the right way"""
     with pytest.raises(escpos.exceptions.Error):
         raise escpos.exceptions.Error("This should raise an error.")