diff --git a/src/pyob/core_utils.py b/src/pyob/core_utils.py
index 6740400..cc467a0 100644
--- a/src/pyob/core_utils.py
+++ b/src/pyob/core_utils.py
@@ -254,7 +254,7 @@ def _get_input_with_timeout(self, timeout: int) -> str:
     def _win32_input(self, start_time: float, timeout: int) -> str:
         import msvcrt  # type: ignore
 
-        input_str = ""
+        input_str: str = ""
         prev_line_len = 0
         while True:
             remaining = int(timeout - (time.time() - start_time))
@@ -282,7 +282,7 @@ def _unix_input(self, start_time: float, timeout: int) -> str:
         import termios
         import tty
 
-        input_str = ""
+        input_str: str = ""
         fd = sys.stdin.fileno()
         old_settings = termios.tcgetattr(fd)
         try:
@@ -393,7 +393,7 @@ def backup_workspace(self) -> dict[str, str]:
                         pass
         return state
 
-    def restore_workspace(self, state: dict[str, str]):
+    def restore_workspace(self, state: dict[str, str]) -> None:
         for path, content in state.items():
             try:
                 with open(path, "w", encoding="utf-8") as f: