diff --git a/conversions/octal_to_binary.py b/conversions/octal_to_binary.py
index 7b1b1aca9..c24fed4e2 100644
--- a/conversions/octal_to_binary.py
+++ b/conversions/octal_to_binary.py
@@ -1,4 +1,4 @@
-def octal_to_binary(octal_number):
+def octal_to_binary(octal_number: str) -> str:
     """
     /**
     * Converts any Octal Number to a Binary Number