diff --git a/cellular_automata/conways_game_of_life.py b/cellular_automata/conways_game_of_life.py
index 079fb4d04..84f4d5be4 100644
--- a/cellular_automata/conways_game_of_life.py
+++ b/cellular_automata/conways_game_of_life.py
@@ -70,7 +70,7 @@ def new_generation(cells: list[list[int]]) -> list[list[int]]:
     return next_generation
 
 
-def generate_images(cells: list[list[int]], frames) -> list[Image.Image]:
+def generate_images(cells: list[list[int]], frames: int) -> list[Image.Image]:
     """
     Generates a list of images of subsequent Game of Life states.
     """